To investigate the effect of occupational exposure to asbestos on mortality, names of all 6292 men born on or after 1 January 1910 and employed as industrial workers in the RN Dockyard, Devonport on 1 January 1947 were submitted to the Office of Population Censuses and Surveys for tracing. Follow-up continued until the end of 1978: over 99% were traced; 3% emigrated; and there were 1043 (17%) deaths. On the basis of the mortality in England and Wales for each five years of age and each five calendar years, the standardized mortality ratio (SMR) was 96. Adjusting the rates for the lower mortality in south-west England, the SMR was 104. No relation was found between SMR and date of birth, and there was only a very slight excess among those more heavily exposed to asbestos. Thirty-one men died with mesothelioma and a further 14 with asbestosis or pulmonary fibrosis. The circulatory disease death rate was slightly raised (SMR = 118), but no more than might have been expected for manual workers. Asbestos-related deaths accounted for at least 4% of all deaths, but probably not many more.