A prominent feature of health in all industrialized countries is the social gradient in health and disease. Many observers believe that this gradient is simply a matter of poor health for the disadvantaged and good health for everyone else, but this is an inadequate analysis. The Whitehall Study documented a social gradient in mortality rates, even among people who are not poor, and this pattern has been confirmed by data from the United States and elsewhere. The social gradient in health is influenced by such factors as social position; relative versus absolute deprivation; and control and social participation. To understand causality and generate policies to improve health, we must consider the relationship between social environment and health and especially the importance of early life experiences.