ORDER

Appellees’ petition for rehearing is granted.

The court’s opinion filed herein on November 16, 1978, is withdrawn and the attached revised opinion substituted therefor.

REVISED OPINION

Appellants brought this diversity action against Daniel C. Olney individually and the *102 law firm of Olney, Levy, Kaplan & Tenner, alleging failure to prosecute properly their personal injury and wrongful death claims. The district court held that the action was barred by Arizona’s two-year statute of limitation for tort claims and granted appellees’ motion for summary judgment. We affirm in part and reverse in part.

I. Facts and Proceedings Below

On July 8, 1969, the husbands of appellants Benally and Begay were killed and appellant Yazzie was injured when the right rear tire of the truck they were riding in blew out, causing the truck to turn over. At the time of the incident, appellant Yazzie and the two decedents were employed by the Union Pacific Railroad Company and were being transported to one of the company’s job sites at Shiprock, New Mexico.

Appellants, who do not speak English and were apparently unfamiliar with the American legal system, sought assistance from an Arizona legal clinic in connection with the accident. They were ultimately referred to the Olney firm for prosecution of their respective claims. However, the only action the Olney firm filed was against the Union Pacific Railroad Company on behalf of appellants Benally and Begay, which was dismissed on October 23, 1973. As a consequence, on July 8, 1971, two years subsequent to the accident, all other possible causes of action apparently became barred by the two-year limitation period on tort claims of Ariz.Rev.Stat. § 12-542.

On June 25, 1974, appellants filed this suit against the Olney law firm. Appellees moved for summary judgment pursuant to the same two-year statute of limitation, arguing that appellants’ claims against the firm accrued on July 8, 1971, when the statute had run on appellants’ wrongful death and personal injury claims. Appellants responded that the two-year tort limitation was tolled by their reasonable failure to discover the facts constituting their causes of action against the law firm until October 23,1973, when the only suit filed by the Olney firm on their behalf was dismissed. 1 They also argued that their complaint stated a cause of action upon a written contract which, under the applicable six-year limitation period of Ariz.Rev.Stat. § 12-548, should not have been dismissed.

The district court held that appellants’ complaint sounded exclusively in tort. The court also held that the applicable two-year tort statute of limitation was not tolled during the time before the injured parties discovered or should have discovered their claims, and accordingly, entered the summary judgment from which this appeal is taken.

II. Standard of Review

Under Fed.R.Civ.P. 56(c), summary judgment is proper only where there is no genuine issue of any material fact or where, viewing the evidence and the inferences which may be drawn therefrom in the light most favorable to the adverse party, the movant is clearly entitled to prevail as a matter of law. Jones v. Halekulani Hotel, Inc., 557 F.2d 1308, 1310 (9th Cir. 1977); Dalke v. Upjohn Co., 555 F.2d 245, 248 (9th Cir. 1977); Handi Investment Co. v. Mobil Oil Corp., 550 F.2d 543, 546 (9th Cir. 1977); Stansifer v. Chrysler Motors Corp., 487 F.2d 59, 63 (9th Cir. 1973). Our role in reviewing the grant of summary judgment is to determine whether there is any genuine issue of material fact underlying the adjudication and, if not, whether the substantive law was correctly applied. Inland Cities Express, Inc. v. Diamond National Corp., 524 F.2d 753, 754 (9th Cir. 1975); Vickery v. Fisher Governor Co., 417 F.2d 466, 468 (9th Cir. 1969).

III. Tort Claim

The district court erred in its determination that the two-year limitation period applicable to appellants’ claims — which it construed as exclusively in tort — could not be tolled by their reasonable failure to *103 discover the facts giving rise to those claims. In Nielson v. Arizona Title Insurance & Trust Co., 15 Ariz.App. 29, 30 , 485 P.2d 853, 854 (1971), the Arizona Court of Appeals stated as the “rule in Arizona”:

Thus, under Arizona law, the question of when appellants knew or should, have known of appellees’ negligence is critical to determining whether the statute of limitation has run.

We believe that the parties’ summary judgment papers present a genuine issue of material fact as to when appellants Be-gay and Benally discovered the alleged malpractice. 2 Appellees note that appellants had been referred to them by a legal services organization. That organization monitored appellees’ efforts, writing to appellees on March 11, 1971:

Appellees argue that because of this monitoring, appellants through their legal services organization knew that appellees did not file suit against other possible defendants prior to the running of the two-year limitation period on-July 8,1971. Appellees conclude that because the instant suit was filed more than two years after July 8, 1971, the suit is time-barred.

Appellants respond that appellees exaggerate the degree of the legal services organization’s monitoring. In their papers before the district court, appellants wrote:

Because the district court erroneously concluded that the discovery ru’e did not apply in Arizona, it did not consider whether there was a material factual dispute regarding when appellants Begay and Benally knew or should have known of the alleged malpractice. The above mentioned contentions show that there are genuine issues of material fact to be resolved. This is particularly so because these disputes involve questions of reasonableness and knowledge, questions this court is especially wary of deciding as a matter of law. We therefore conclude that the district court erred in granting defendant’s partial summary judgment as to appellants Begay and Benally.

IV. Contract Claim

Appellants claim that even if their tort claims are barred by the statute of limitations (as are those of appellant Yazzie), *104 3 their complaint also stated a claim upon a written contract subject to a six-year limitation period under Ariz.Rev.Stat. § 12-548. Because they filed the instant lawsuit within six years of July 8, 1971, appellants conclude that their contract claims are not time-barred.

In Beane v. Tucson Medical Center, 13 Ariz.App. 436 , 477 P.2d 555 (1971), 4 plaintiffs had expressly set forth in their complaint both contract and tort claims. They acknowledged that their tort claims were time-barred. They argued that their contract claim — that a hospital had breached contractual obligations by providing inadequate postoperative care and treatment— should fall within the six-year written contract limitation period. The Arizona Court of Appeals wrote:

Id. at 438 ; 477 P.2d at 557 (emphasis in original). 5

In the present case the wiitten contracts between each appellant and appellees provided in relevant part that the appellant “do[es] hereby retain the law firm . to represent me and my children in an action for damages against the parties responsible for my injuries” or those of my husband. 6 Appellants now claim that the *105 Olney firm failed to file suits against the proper parties and failed to prosecute properly the Union Pacific suit. Bound as we are to follow the law of Arizona, we must conclude that Beane means that the statute of limitations for an- action upon a written contract does not apply to appellants’ claims.

V. Conclusion

As to appellants Begay and Benally, there is a genuine issue of material fact as to when they discovered the alleged malpractice, and hence when the tort limitation period began to run. As to them, the district court’s granting of summary judgment is reversed. The district court’s granting of summary judgment as to appellant Yazzie is affirmed.

AFFIRMED IN PART, AND REVERSED AND REMANDED IN PART.

. In addition, according to the district court’s Memorandum and Order of October 27, 1975, appellants did not discover until December 20, 1974 — in the course of a deposition. — -that the Olney firm “had intentionally not filed an action” against one potential defendant.

. In their papers filed in the district court, appellants’ attorneys acknowledged that

. See note 2 supra.

. Since jurisdiction in this case is based on diversity of citizenship, and since the material events alleged by appellants occurred within the state of Arizona, this court is bound to apply the substantive law of that state. See Klaxon Co. v. Stentor Elec. Mfg. Co., 313 U.S. 487, 496 , 61 S.Ct. 1020 , 85 L.Ed. 1477 (1941); Erie R. R. Co. v. Tompkins, 304 U.S. 64, 78-80 , 58 S.Ct. 817 , 82 L.Ed. 1188 (1938).

. In Kain v. Arizona Copper Co., 14 Ariz. 566, 569-70 , 133 P. 412, 414 (1913), the Arizona Supreme Court wrote:

. Each appellant signed the following agreement on September 30, 1970: