BACKGROUND: The adverse effect on health of poor social circumstances might accumulate not only over the lifespan of the individual but also across generations. This study examines the effect of parent's and grandparent's socioeconomic position on all-cause mortality of their adult offspring. METHODS: 2890 males born in the metropolitan area of Copenhagen, Denmark in 1953, whose mothers were interviewed for information on family social background in 1968, were followed from 1968 to 2002 for information on vital status by record linkage to the Civil Registration System. The data were analysed using Cox regression models. RESULTS: All-cause mortality from age 15 to 49 years increased 25% [95% confidence interval (CI) 13-39%] for each number of parents or grandparents from working or unknown occupational social class. Offspring mortality decreased with the number of ancestors with a secondary school education hazard ratio [HR = 0.84 (95% CI 0.76-0.93)]. When the cumulative measures of ancestor's occupation and education were included in the same model, the estimates for the effect of occupational social class [HR = 1.19 (95% CI 1.06-1.34)] and education [HR = 0.91 (95% CI 0.80-1.03)] both attenuated. These relations only changed slightly when subject's own occupational class at age 22 years was taken into account. CONCLUSION: The adverse health effects of disadvantaged social circumstances accumulate not only over an individual's lifespan but also across generations. Cumulated occupational social class of ancestors seems to be an independent predictor of mortality in adult life after adjustment for subject's own social class at age 22 years.