The study is based on 3990 men and women exposed to asbestos dust for at least three years at their place of work, and prospectively and epidemiologically examined since 1 January, 1977. By 31 December, 1983, 336 had been registered as having died. Calculation of standard mortality rates indicates that the incidence of malignant tumour as cause of death was much higher than in the general population of the FRG, that of fatal mesothelioma about 100 times as high. Standard mortality rate for lung cancer was increased by 48% and 175%, respectively, depending on whether exposure to asbestos dust had ended after (subgroup I) or before (subgroup II) 1 January, 1972. Proportional mortality rate of 43% of tumours at all locations, with about 14% lung cancer and about 9% fatal mesothelioma cases in subgroup II, approaches the internationally recognized frequency of asbestos-associated tumours.