This paper investigates the effect of health selection and its contribution to the social class gradient in health. Both inter- and intra-generational mobility were examined. Longitudinal data on health and social class at three life stages (16, 23, 33 years) are from the 1958 British birth cohort. Individuals with poor health were more likely to move down and less likely to move up the social scale, especially at the inter-generational transition. The effect of health selection on the social gradient was variable, of modest size and cannot be regarded as a major explanation for inequalities in health in early adulthood.