From the general population in the county of Uppsala, Sweden, 1,596 men with pleural plaques fulfilling strict radiologic criteria were identified from 1963 until June 1985. The men have been followed prospectively for 16,369 person-years. The number of mesotheliomas and bronchial carcinomas was compared with the age- and year-specific expected incidence from the official cancer registry of Sweden. Fifty bronchial carcinomas occurred, while 32.1 were expected after correction for smoking habits, a difference which was statistically significant. Patients with radiologic asbestosis were overrepresented among those with bronchial carcinoma. The risk for patients with pleural plaques without asbestosis was increased 1.4 times, which was statistically significant. There were 9 mesotheliomas, while only 0.8 were expected. The mean latency time from first exposure to diagnosis of bronchial cancer was 44.1 years and for mesothelioma was 48.1 years. Thus, pleural plaques on the chest roentgenogram indicate significant exposure to asbestos, with an increased risk for mesothelioma and possibly also for bronchial carcinoma. Any person found to have plaques on chest roentgenogram should be informed of them and should be persuaded to stop smoking.