*228 OPINION

In this proceeding under the Interlocutory Appeals Act of 1958, 28 U.S.C. § 1292 (b), we are called upon to decide by means of an ■ interlocutory appeal whether this suit may be maintained as a class action under Rule 23, Federal Rules of Civil Procedure. The action was brought by plaintiffs Richard and Margo Kline, husband and wife, on behalf of themselves and all sellers of residential real estate in Los Angeles County against the Los Angeles Realty Board and its several divisions and 32 named real estate brokers representing a class consisting of all real estate brokers who were members of the Board during the 4-year period prior to the filing of the action.

Plaintiffs allege that the Board and its members conspired in violation of section 1 of the Sherman Act, 15 U.S.C. § .1, to fix brokerage commissions through distribution of a recommended fee schedule to its members. Plaintiffs claim that the fee schedule fixed commissions at a higher rate than it would have been absent the schedule, causing damage to plaintiffs which they are entitled to have trebled under section 4 of the Clayton Act, 15 U.S.C. § 15 . During the 4-year period involved, approximately 800,000 deeds were recorded in Los Angeles County. Based upon this fact defendants estimated that upwards of 400,000 sales with approximately that number of plaintiffs could well be involved in this class suit. 1 By virtue of the alleged conspiracy and the damages sustained the plaintiffs prayed for a judgment against the defendants as a class and each of them individually totaling $250 million actual damages trebled to $750 million or according to the proof adduced at trial, together with a reasonable attorney’s fee and costs of suit.

More than 2,000 brokers who were members of the Los Angeles Realty Board and its divisions performed services during the 4-year period in the sale of residential property, which is defined as any lot or parcel of real property improved with from 1 to 12 dwelling units. Defendants denied participating in any conspiracy. The defendant Board admitted publishing and distributing a commission schedule but denied that any member was required to follow it. The fee schedule suggested a commission of six percent of the total purchase price. The foreward of the schedule states in part:

The trial court received a motion for certification of the action as proper under Rule 23. After having considered the motion, the opposition, voluminous supporting documents and filings and after having heard extensive argument, the district court granted the motion in part and denied it in part to the following effect:

(1) The named plaintiffs Richard and Margo Kline, husband and wife, were found to be representative of a class of all persons who sold residential property within Los Angeles County, California, during the period September 24, 1966, to September 23, 1970, and used the services of one or more of the named defendant real estate brokers or brokerage firms or any member of the Los Angeles Realty Board (including its divisions) and compensated said brokers or firms for their services.

(2) The 32 named defendant real estate brokers and brokerage firms together with the Los Angeles Realty Board and its branches were determined to be representative of a defendants’ class of all real estate brokers who during the *229 same period were members of the Los Angeles Realty Board including its branches and who acted in that capacity in connection with the sale of residential real property.

(3) The district court denied Martin Simon status as a representative of a class of “unsuccessful sellers of real property,” because it would have been inappropriate under Rule 23.

(4) The court also denied representative status to sellers of commercial and industrial property.

The court’s two findings of representative status were based in part on its determination that the central issue concerned whether there was a conspiracy entered into by the defendants to fix prices for commissions in sales of residential real property in Los Angeles County. This issue, the court found, presented common questions of law and fact which predominated over any questions of law and fact affecting only individual members of the classes. A subis-sue, ruled the court, was whether there was a schedule of commissions prepared, published and distributed by the defendants and whether said schedule was substantially adhered to by the broker defendants. This central and subissue should not have to be tried on more than one occasion, said the court, and although individual issues did exist such as whether the individual brokers knew of the schedule and whether they conformed to it, these individual issues did not predominate over the common issues of law and fact. The court having concluded that its order involved a controlling question of law as to which there was a substantial ground for difference of opinion, certified it for immediate appeal under 28 U.S.C. § 1292 (b). This court has entered its order permitting the appeal. 2 Defendants appeal the district court’s order finding the case to be proper class action.

Without expressly so stating, the parties appear in agreement that whether this is a proper class action is to be determined under Rule 23(b)(3). We are in accord. 3 Rule 23(b) first requires that *230 the prerequisites of Rule 23(a) must be satisfied. They are (1) that the class is so numerous that joinder of all members is impracticable, (2) there are questions of law or fact common to the class, (3) the claims or defenses of the representative parties are typical of the claims or defenses of the class, and (4) the representative parties will fairly and adequately protect the interests of the class. The propriety of the certification of both plaintiff and defendant classes and of the class action in general must be measured against these requirements.

It appears clear that prerequisites (1) and (2) are satisfied by both classes, and no question has been raised as to the adequacy of representation under (4). Although Mr. and Mrs. Kline represent some 400,000 sellers, they are sellers who have employed one of the defendant class members; there are 32 named brokers and brokerage corporations as well as the Los Angeles Realty Board and its branches as defendants, and it can well be assumed that the other 2,000 defendants are adequately represented by them. Whether the claims or defenses of the representatives of the named parties are typical of all the claims and defenses of the absent members of the two classes will be considered under subsection 23(b)(3), since to a considerable extent the criteria are similar. We consider, then, the additional requirements of Rule 23(b)(3): (1) whether common questions predominate over individual ones; and, (2) whether the action is “manageable.”

I. Whether the Questions of Law or Fact Common to the Members of the Class Predominate Over Any Questions Affecting Only Individual Members.

The crux of defendants’ argument is that individual questions concerning the liability of each individual broker defendant and the injury of each individual plaintiff predominate over any common questions of a conspiracy. The plaintiffs adversely contend that they can prevail on a legal theory which avoids individualized issues of defendant liability, which establishes plaintiff injury in general, and which leaves the determination of the quantum of individual recovery to a mechanical process or to separate adjudication. In short, appellees argue that they can prevail on a generalized antitrust theory (utilizing “per se” rules) while the appellants deny this and argue that individual issues must be litigated. Resolution of this controversy requires an examination of substantive antitrust law.

In order to prevail under section 1 of the Sherman Act, 15 U.S.C. § 1 , and to recover treble damages under section 4 of the Clayton Act, 15 U.S.C. § 15 , the plaintiffs must prove both that the defendants’ conduct contravened section 1 *231 and that the plaintiffs suffered injury as a direct result of this illegal conduct. 4 Each of these two facets will be separately considered.

A. Establishing illegal defendant conduct.

The appellees advance two theories under which they contend that they can establish illegal conduct without individualized proofs. Both theories are based upon trade association practices and can be called the “Membership-Ratification” theory and the “Adherence” theory. The former relies heavily upon Phelps Dodge Refining Corp. v. FTC, 139 F.2d 393, 396-397 (2d Cir. 1943), which stated:

Since Phelps Dodge the “Membership-Ratification” theory has been reformulated by numerous courts including this circuit. In each of these reformulations much of the stress falls upon the knowledge component. In Riss & Co. v. Association of American Railroads, 187 F.Supp. 306, 312-313 (D.D.C.1960), the court said:

In Vandervelde v. Put & Call Brokers & Dealers Association, Inc., 344 F.Supp. *232 118, 155 (S.D.N.Y.1972), it was recently stated:

This court considered the issue in Northern California Pharmaceutical Association v. United States, 306 F.2d 379 (9th Cir.), cert. denied, 371 U.S. 862 , 83 S.Ct. 119 , 9 L.Ed.2d 99 (1962). That was a criminal case. The indicted defendants were the association, an incorporated California trade association, and one Donald Hedgpeth. The members themselves were not parties to the proceeding as defendants and to this extent the case becomes dissimilar. Hedgpeth, a pharmacist, prepared a price schedule for noncompounded prescriptions which the corporation distributed to its members. In connection with the evidence required to convict the two defendants who were indicted the court said:

It thus clearly appears that in order for a member of a trade association to become guilty in a criminal case or liable in a treble damage case he must have “knowingly, intentionally and actively participated in an individual capacity in the scheme.”

Plaintiffs’ reliance upon this case and Plymouth Dealers’ Association of North California v. United States, 279 F.2d 128 (9th Cir. 1960), to prove liability by continued membership is mistaken. In Plymouth Dealers’ Association the action was a criminal prosecution against the association, a corporation. There, again, the court approved instructions which required the jury in order to convict to find that there was an agreement “that the defendant should formulate retail list prices for Plymouth motor cars” and “that the price schedules so agreed upon were a substantial part of the price structure used in the sale of Plymouth motor cars.” Id. at 130 n. 3. But the court in speaking of “the defendant,” was referring only to the indicted corporate defendant, i. e., the Dealers’ Association. The liability vel non of the association members was not in issue because they were not defendants although they were described as co-conspirators. Nor is there any indication from the opinion that the dealer members were parties in any agreement.

We would read Plymouth Dealers’ Association as elaborated by Northern California Pharmaceutical Association as establishing the law of this circuit that the printing of a price schedule and its distribution to members is not enough to establish civil or criminal liability. Proof here, therefore, even by admission of the Realty Board that it prepared a suggested commission schedule and distributed it to its members does not establish the illegal conduct necessary for a recovery.

Plaintiffs also rely heavily upon United States v. National Association of Real Estate Boards, 339 U.S. 485 , 70 *233 S.Ct. 711 , 94 L.Ed. 1007 (1950). In that action the Supreme Court stated:

There is no evidence here of such an ethic or such an agreement. The Court went on to say:

Thus, the Real Estate Boards case would appear to require for a per se violation by members (1) .an agreement and (2): adherence or consensual approval. In fact, the Court declined to reverse a district court’s finding that two of the defendants, the National Association and one Herbert Nelson, were not participants in the conspiracy upon the basis that the code of ethics of the National Association, that the fee schedule “should be observed,” was somewhat ambiguous. Said the Court, “it may be advisory only.” Id. at 495 .

So we cannot be persuaded that in this case proof of conspiracy or proof of illegal conduct of each defendant may be accomplished by generalized means. The legal significance of the written document and the rules or bylaws of the Realty Board and the method of compiling the document may indeed be a question of law and fact common to all defendants. But membership liability is inherently an individual question. It cannot be answered by generalized “Membership-Ratification” (mere continuation of membership) of any type suggested by appellees.

Plaintiffs have also misused the “Adherence” theory. Under this approach if Broker A receives the fee schedule and follows it in his pricing, Broker A would be liable as having adhered to the conspiracy. The fact that Broker A has adhered does not, however, prove that Broker B did so. Nor does the fact that a “substantial” number of brokers adhered prove that Broker B did so also. None of the cases cited by appellee establishes that mere parallelism conclusively establishes liability. Northern California Pharmaceutical Association, supra, holds to the contrary. Once again, this issue involves individual questions and necessarily invites individual defenses. Each defendant is clearly entitled to come forward and prove that he did not know of the commission schedule or that he opposed it or ignored it or, perhaps, some other yet unknown defense.

On the question of the defendants’ illegal conduct no adequate showing has been made that the questions of law or fact common to the members of the class predominate over the questions affecting individual members.

B. Establishing the plaintiffs’ injury, i. e., the damages ' issue.

In order to certify the action as a proper class action it is necessary to demonstrate that the class action is superior to other available methods for the fair and efficient adjudication of the controversy as required by Rule 23(b)(3). Proof of injury is an essential substantive element of the successful treble damage antitrust action. Gray v. Shell Oil Co., 469 F.2d 742, 748 (9th Cir. 1972), cert. denied, 412 U.S. 943 , 93 S.Ct. 2773 , 37 L.Ed.2d 403 (1973); Winckler & Smith Citrus Products Co. v. Sunkist Growers, Inc., 346 F.2d 1012 , 1014 n. 1 (9th Cir.), cert. denied, 382 U.S. 958 , 86 S.Ct. 433 , 15 L.Ed.2d 362 (1965). Here there was apparently no showing made in support of the question whether “economic reality” might dictate that this action proceed as a class action or not at all. Eisen v. Carlisle & Jacquelin, 416 U.S. 156 , 94 S.Ct. 2140 , 40 L.Ed.2d 732 (1974). *234 The matter is not discussed in the briefs. The prayer for estimated damages indicates that in many instances the damages if recoverable would be substantial. The fact that sales of 12-unit complexes are included in the disputed transactions also points in that direction. 5 Thus the potential benefit to the proposed class by the use of Rule 23 does not rise to the same dimension as those where the damage award sought is only $70. Eisen v. Carlisle & Jacquelin, supra, or $2, In re Hotel Telephone Charges, 500 F.2d 86 (9th Cir. 1974). It is also entirely probable that a goodly number of the total transactions would not be litigable for one reason or another; 6 and, of ’course, some of the larger brokers and brokerage firms could reasonably be expected over the 4-year period to have a substantial number of residential transactions which would be involved in a single action against that one defendant; and finally, some of the absentee plaintiffs might not desire to become involved in the litigation at all.

The allegation is that from the 400,000 to 800,000 transactions during the period in question damages will be proved in excess of $250 million which trebled will aggregate $750 million. In addition, plaintiffs are asking for costs and attorneys’ fees. All of these elements of recovery are within the provision of 15 U.S.C. § 15 . The amounts are staggering. In addition, the prayer is for recovery against the defendants jointly and severally. State of Washington v. American Pipe & Construction Co., 280 F.Supp. 802 (S.D.Cal.) mandamus denied sub nom., American Pipe & Construction Co. v. Pence, 393 F.2d 568 (9th Cir.) (unrelated issue), cert. denied, 393 U.S. 842 , 89 S.Ct. 122 , 21 L.Ed.2d 113 (1968). This means that the small individual operator faces a potential liability of upwards of three-quarters of a billion dollars for which all of his or her assets are responsible. The amount of a recovery in a lawsuit is not ordinarily of concern where a wrong has been inflicted and an injury suffered. But when 2,000 are joined in an action in which each is jointly and severally liable, the liability is increased in geometric ■ progression. Such an award against each of 2,000 real estate broker defendants would shock the conscience.

In somewhat similar circumstances, class actions have sought outrageous amounts in statutory penalty cases such as the $100 minimum under the Truth in Lending Act of 1968. Ratner v. Chemical Bank New York Trust Co., 54 F.R.D. 412 (S.D.N.Y.1972) (aggregate of $13 million sought); Shields v. First National Bank of Arizona, 56 F.R.D. 442 (D.Ariz. 1972) (aggregate of $100 million sought); Alsup v. Montgomery Ward & Co., 57 F.R.D. 89 (N.D.Cal.1972) (aggregate of $20 million sought in one consolidated case and $8 billion in another); Gerlach v. Allstate Insurance Co., 338 F.Supp. 642 (S.D.Fla.1972) (aggregate of approximately $1 billion sought). In each case cited the district court denied class action treatment. Judge Frankel in Ratner among other reasons stated:

This court stated in LaMar v. H & B Novelty & Loan Co., 489 F.2d 461 (9th Cir. 1973):

We find that the same reasoning applies to treble-damage actions under the Sherman and Clayton Acts. Under those statutes compensatory damages must be trebled, Locklin v. Day-Glo Color Corp., 429 F.2d 873, 878 (7th Cir. 1970), cert. denied, 400 U.S. 1020 , 91 S.Ct. 582 , 27 L.Ed.2d 632 (1971). The trebling of damages in such cases is a statutory punitive measure. As expressed by Judge Learned Hand in Lyons v. Westinghouse Electric Corp., 222 F.2d 184, 189 (2d Cir.), cert. denied, 350 U.S. 825 , 76 S.Ct. 52 , 100 L.Ed. 737 (1955), “. . two thirds of the recovery is not remedial and inevitably presupposes a punitive purpose.” The intent of Congress under section 4 of the Clayton Act, 15 U.S.C. § 15 , appears to have been to impose punishment upon the violator of section 1 of the Sherman Act for his own malefactions not to subject him to vicarious liability by the coincidence of a class action for the staggering damages of the multitude. For example, if the sole enterprise real broker with a small suburban business finds that out of $10,000 in commissions he has earned in the year past, $1,000 has been determined to consist of overcharges for which in an antitrust action, he becomes obligated to pay $3,000 as treble damages. But because he joined a realty board and received and followed suggestions as to proper commissions he is now obligated legally to pay $750 million. At some point the logic of the law leads in this situation to an ad absurdum result. We believe this is it. 7 In the light of the problems engendered by the requirement of proof of damages, we cannot find that under Rule 23(b)(3) this class action is superior to other available methods for the fair and efficient adjudication of the controversy.

II. Manageability of the Action.

The final consideration for class action status involves the question of manageability under Rule 23(b)(3)(D), i. e., “the difficulties likely to be encountered in the management of a class action.” This problem was recognized by the Advisory Committee’s Notes on the Proposed Amendments to Rules of Civil Procedure, 39 F.R.D. 69 , 103 (1966), where the Committee discussed the types of cases which would generally qualify under the rule. It then by way of reservation pointed out that certain cases would be inappropriate as class actions stating as an example that a mass accident,

Here, as the plaintiffs state in their brief, they do not rely upon the “isolated fact of membership” in the Realty Board nor upon “mere conscious parallelism” of the members.

But this is only the plaintiffs’ case as to an individual defendant. There are 2,000 defendants. Perhaps such evidence would establish a prima facie case. But the defendant would then have the right to come forward and submit his proof; 8 he may categorically deny some of the proof of the plaintiffs or may submit matter in avoidance. This trial must repeat itself with individual differences some 2,000 times as far as we can discern based upon the pleadings before us now. There are some questions that would need be proved only once such as the distribution of the schedule, but there are other matters which would have to be gone into as many times as there were sales by that defendant during that 4-year period. One jury could obviously not try the facts as to all defendants. There is a serious question whether such ordinary trials could properly be referred to a master. And then, after the case on liability is submitted or tried, the same procedure would have to be followed as to damages. 9 It would appear that generalized treatment would soon fall into individualized law suits. At that point the actions become unmanageable as a class action.

For the foregoing reasons we conclude that the present action is unsuitable for class action treatment. We note that in making this determination we intimate no judgment on the merits.

The judgment of the trial court that the action may be tried as a class action is reversed.

. The plaintiffs did not disagree but suggested at oral argument as a word of caution that there might be more.

. Although questions were raised as to the application of the Interlocutory Appeals Act to the order of the trial court certifying the appeal as an interlocutory one, those questions were briefed by counsel on both sides and the order granting permission to submit an interlocutory appeal was granted by another panel of this court. We do not further examine that question.

. Rule 23(b) states in pertinent part:

As originally enacted, Rule 23 would not have accommodated a suit like that filed here. It provided only for a “true class suit” in which, but for the rule, the joinder of all interested persons would have been essential, 3B J. Moore, Federal Practice 1] 23.08 (1974); the “hybrid” class suit where the interests of the parties were several but concerned a specific property, id. lj 23.09; and the “spurious” class suit where there was no jural relationship between the parties but a common question of law or fact existed. Such an action was an invitation to those having such an interest to join but not a requirement that they accept. Id. j[ 23.10. The importance of Rule 23 at this time was not outstanding. In 1966 the rule was amended to provide a more flexible remedy. Recoveries would be available for or on behalf of all members of the class and the judgments binding upon all provided the requirements of the rule were met. The popularity of class actions increased fourfold within a period of 4 years and developed a host of champions and critics. Compare Blecher, Is the Class Action Rule Doing the Job? (Plaintiff’s viewpoint), with Simon, Class Actions — Useful Tool or Engine of Destruc *230 tion, 55 F.R.D. 365 , 375 (1973). The courts have had their own difficulties in solving the problems generated by the rule. Eisen v. Carlisle & Jacquelin, 370 F.2d 119 (2d Cir. 1966), cert. denied, 386 U.S. 1035 , 87 S.Ct. 1487 , 18 L.Ed.2d 598 (1967) (Eisen I); Eisen v. Carlisle & Jacquelin, 391 F.2d 555 (2d Cir. 1968) (Eisen II); and Eisen v. Carlisle & Jacquelin, 479 F.2d 1005 (2d Cir. 1973), vacated, 416 U.S. 156 , 94 S.Ct. 2140 , 40 L.Ed.2d 732 (1974) (Eisen III).

The Supreme Court at the last term, October 1973, passed upon two cases involving the scope of class actions. Zahn v. International Paper Co., 414 U.S. 291 , 94 S.Ct. 505 , 38 L.Ed.2d 511 (1973), held that a diversity action seeking damages could not be maintained on behalf of unnamed plaintiffs whose claims did not meet the jurisdictional amount requirements. Eisen v. Carlisle & Jacquelin, 416 U.S. 156 , 94 S.Ct. 2140 , 40 L.Ed.2d 732 (1974), upheld the decision of the Court of Appeals in Eisen III, supra, that individual notice must be given to all identifiable members of the class at the plaintiffs expense and that a preliminary or “mini-hearing” on the merits to determine whether it might be maintained as a class action was improper.

Our own court has had more than one occasion to consider the problems of Rule 23 as amended. Most recently we have had before us La Mar v. H & B Novelty & Loan Co., 489 F.2d 461 (9th Cir. 1973), and In Re Hotel Telephone Charges, 500 F.2d 86 (9th Cir. 1974).

. 15 U.S.C. § 1 states:

15 U.S.C. § 15 states:

. Assuming 400,000 transactions causing damage by excess commissions in the estimated sum of over $250 million the average recoverable damage amounts to $625. Trebled, the individual recovery would amount to $1,875 and the aggregate to $750 million the amount of the prayer. To arrive at that average figure, obviously many damage claims have been estimated that would result in a figure considerably in excess of that average. Since attorneys’ fees and costs are also recoverable in a successful 15 U.S.C. § 15 action, it may be safely assumed that a great many of the cases could be separately prosecuted.

. Affidavits of some defendants in the file vehemently assert that they did not follow the Board’s suggestions; others may assert other defenses which would make litigation of a claim a poor plaintiffs risk.

. As pointed out in a slightly different context in Green v. Wolf Corp., 406 F.2d 291, 303 (2d Cir. 1968), cert. denied, 395 U.S. 977 , 89 S.Ct. 2131 , 23 L.Ed.2d 766 (1969):

. It has been suggested that generalized proof of damages might suffice under Rule 23. But the rule does not eliminate the ultimate need for individual proof of damages by each member of the class. Nor does it foreclose the right of each defendant to assert his defenses before a jury if one is requested.

28 U.S.C. § 2072 states in pertinent part:

. Again, generalized proof is suggested, as presumably a witness would testify as to what was a fair commission absent the schedule. But the defendant as to each transaction would be entitled to give his particularized version. The suggested commission schedule by its terms applies to “normal” sales.