Summary Research has suggested that social-class differences in adult health may be at least partly determined by conditions earlier in life. In 2636 Finnish men, we assessed impact of childhood and adult socioeconomic conditions on adult mortality risk by examining whether differing socioeconomic lifecourses from early childhood to adulthood were associated with different risks of all-cause and cardiovascular mortality. Compared with high-income adults, those with low income had increased relative risks of all-cause (2.54, 95% Cl 1.83-3.53) and cardiovascular (2.37, 1.51-3.7) mortality, but these increased risks were not related in either adult group to childhood socioeconomic conditions. Men who went from low-income childhood to high-income adulthood had the same mortality risks as those whose socioeconomic circumstances were good in both childhood and adulthood (1.14, 0.56-2.31, all causes; 0.99, 0.39-2.51, cardiovascular). By contrast, men who experienced poor socioeconomic circumstances as both children and adults were about twice as likely to die as those whose position improved (2.39, 1.28-4.44, all causes; 2.02, 0.9-4.54, cardiovascular). Our findings suggest that socioeconomic conditions in childhood are not important determinants of adult health. We caution against this interpretation – a lifecourse approach to socioeconomic differences in adult health requires understanding of the social and economic context in which individual lifecourses are determined.; Poor socioeconomic status in childhood may affect health in adulthood. Researchers reviewed information on the socioeconomic status in both childhood and adulthood for 2,636 Finnish men. During the study, 85 of 166 deaths were due to cardiovascular disease. Compared with high-income adults, men with low incomes were about 2.5 times more likely to die of all causes combined and 2.4 times more likely to die of cardiovascular disease. However, these increased risks of death were not related to childhood social conditions. The risk of death during adulthood was similar among high-income adults with either a low-income or high-income childhood. In contrast, men who had poor socioeconomic conditions as both children and adults were about 2.4 times more likely to die from any cause and about two times more likely to die from cardiovascular disease than men whose socioeconomic status improved during adulthood.