Although it is well known that their sex and socio-economic position profoundly influence people's mental and physical health, their use of health care, and their likely length of life, much research uses sex and social class as control variables rather than enquiring into the reasons for their association with health. Recent work on socio-economic differentials in health shows that these exist in all societies and are apparent throughout the social scale, suggesting that there is not simply a threshold of absolute deprivation below which people are sicker, but a linear relationship between socioeconomic circumstances and health even among the better-off. Other recent work indicates that cultural, social and economic conditions in the past may help to explain current variations in health. The observation that there are variations over the life course in the social patterning of health raises a number of interesting questions about the mechanisms involved; all the likely explanations have a social component. There is currently an exciting agenda for studying questions about interactions between material, psychosocial and biological factors in the production of health. Answers to such questions are important for decisions about how, when, and on whom public health medicine should intervene to promote the public health and to reach the targets set in the recent White Papers.