An epidemiologic and cause-related study was done in Tuzköy, a small village in the city of Nevşehir, in the Anatolian region of Turkey. The neighboring village of Kizilböy was used as a control. People 25 years of age or older were studied: 312 persons (145 males and 167 females) from Tuzköy and 95 persons (45 males and 50 females) from the control village. The annual incidence of malignant pleural mesothelioma (MPM) was found to be 6.5 cases (22 cases per 10,000 people) in Tuzköy. Several other respiratory disorders were detected as well. Although no type of asbestos could be found in Tuzköy and its vicinity, the asbestiform mineral zeolite was found in soil samples from the roads and fields of Tuzköy, in its building stones, and in lung tissues of the villagers. Chest X-rays revealed no cases of MPM or other respiratory abnormalities in the control group. No zeolite could be found in the control village. Therefore, zeolite was thought to be the cause of MPM and the other respiratory disorders in Tuzköy.