Mortality studies show that social inequalities in health include, but are not confined to, worse health among the poor. There is a social gradient: mortality rises with decreasing socio-economic status. Three large sample studies, one British and two American, brought together for their complementarity in samples, measures, and design, all show similar social gradients for adult men and women in physical and mental morbidity and in psychological well-being. These gradients are observed both with educational and occupational status and are not explained by parents' social status or lack of an intact family during childhood. They are also not accounted for by intelligence measured in school. This suggests that indirect selection cannot account for inequalities in health. Possible mediators that link social position to physical and mental health include smoking and features of psycho-social environment at work and outside.