Between 1981 and 1985 seven patients from three villages of the Metsovo area in Northwestern Greece (population 5000) developed malignant pleural mesothelioma (MPM). The diagnosis was made with pleural biopsy and pleural fluid cytology. Six of these patients have died 18-24 months after the first symptoms (usually dyspnea on exertion) and 1 is still alive after 24 months. Seven MPMs in 5,000 in five years is about 280 times the expected incidence of 1/1,000,000/year. In the same area, endemic pleural calcifications linked to nonoccupational asbestos exposure have recently been reported, but none of our patients with MPM had pleural calcifications. The combination of MPM and pleural plaques in such a high frequency in the same area strongly suggests asbestos fiber as a common etiologic agent. On the other hand, the fact that the combination of MPM and pleural plaques did not occur in the same individuals, suggests a different response to this common offending agent.