OBJECTIVES: This study aims at examining whether the relation between established risk factors and mortality differs with socioeconomic status as measured by level of education. METHODS: A population-based sample of 14,399 women and 16,236 men aged 20-93 years from Copenhagen was stratified into three educational levels measured as basic schooling, and the effect of smoking habits, alcohol consumption, physical activity, and body mass index, respectively, on mortality was assessed. RESULTS: Those with the lowest level of education were most frequently heavy smokers, heavy drinkers, physically inactive, and obese. During a mean follow up of 16 years 10,952 subjects died. Compared with subjects with the lowest educational level, women with the highest educational level had a relative risk of 0.80 (95% CI; 0.70-0.91), and men of 0.71 (0.65-0.78). Heavy smoking compared with never smoking implied a more than twofold increased risk at all three educational levels among both men and women. The relation between alcohol intake and mortality was J-shaped on all three educational levels. There were decreasing risk functions describing the relations between physical activity and mortality on all three strata. Further, subjects who were either very lean or obese had increased risks of death compared with those of normal weight at all educational levels in both genders. CONCLUSIONS: The difference in distribution of the main known risk factors may be part of the explanation for the differences in mortality risk. However, these risk factors seem to influence mortality equally at different educational levels. Therefore, social inequalities in mortality do not seem to be explained only by differences in effect of lifestyle risk factors, but are also related to the social rank or unexamined factors within.