The debate about social inequality in health in Britain has so far been based principally on mortality rates. A survey of morbidity and fitness in a large representative sample of adults living in private households in England, Wales, and Scotland reveals striking differences between social classes in self-defined health status, the reported incidence of illness, the prevalence of chronic disease, and measured physiological fitness. The disadvantage in health status does not simply relate to a minority in the poorest social circumstances but appears to be related in a very regular way to the social class structure.