We have argued that a combination of the factors reviewed may account for inequalities in health, both within and between countries. The situation is complex, but not impossibly so. Much progress has been made in sorting through potential explanations. The Whitehall studies have been used to illustrate these possible explanations. There is only a unifying explanation to the extent that social position is related to a number of factors: differences in early life experience, differences in behavior, differences in material conditions, and differences in psychosocial factors. Often investigations focus on just one of these issues, and thus fail to explore the other factors, making interpretation difficult. Although there may be multiple factors operating, one is drawn back to the observation that the social class differences apply to CHD and most causes of death. The challenge for researchers in this area is to develop the methodology for exploring the interrelationships and interactions between the influences on health occurring throughout the life course. Only then will it be possible to separate out the relative importance of the various potential explanations for socioeconomic differentials in CHD and other diseases, which is crucial for planning the strategies to counter them.