One of the major health problems facing industrialized countries is the persisting social class differences in the rate of occurrence of the major chronic diseases. It is true in the United States as it is in the United Kingdom, Scandinavia, Japan, and other countries. The advantage of investigating these social differences in the United Kingdom is that they have been most extensively documented, but findings are likely to be generalizable. The Black Report comprehensively reviewed the persisting social inequalities in health and concluded that the reasons were not completely understood. The Whitehall Study of the British civil service confirms the social gradient in mortality.