Total mortality, mortality from coronary heart disease (CHD), cerebrovascular disease, and other causes of death, were examined for three social groups and ten socio-economic groups in Sweden. The study included all subjects born in the country between 1896 and 1940 who were economically active in 1960-1.9 million men and 0.7 million women. Information on social and socio-economic status, and other social and demographic characteristics, was obtained from the 1960 Census. Information on cause-specific mortality during the period 1961-68 was obtained from a record linkage with the Cause of Death Registry. The analyses were based on 112,469 deaths and 21 million person years at risk. Information on smoking habits was obtained from a sample of 55,000 from the Census population. CHD mortality for women was high among manual workers, SMR = 110 (95% confidence limits 104-117), and low among non-manual workers, SMR = 84 (78-91). CNS-vascular mortality for women was also high among manual workers, SMR = 107 (110-115), and low among non-manual workers, SMR = 89 (82-97). Heavy smoking was more common among non-manual workers in both sexes, which may have contributed to a reverse social class gradient among men, with non-manual male workers being at higher risk for CHD than manual male workers. Farmers (and agricultural workers) generally had a low mortality. Other self-employed men and women had a high total mortality, a high mortality from CHD and CNS-vascular disease--and a high proportion of heavy smokers. There remain differences in mortality between social and socio-economic groups which cannot be explained by smoking habits, age, gender, urbanization, region of residence and martial status.