Consistent with international evidence, the findings of Australian research show that socioeconomically disadvantaged groups experience significantly higher mortality and morbidity rates. Despite marked improvements in the health of all segments of the Australian population in recent decades, during this same period there has also been an increase in socioeconomically related mortality inequalities for some conditions. Socioeconomically disadvantaged groups are more likely to engage in health-damaging behaviours, experience poorer psychosocial health, make less use of the healthcare system for preventive purposes, and have a more adverse risk factor profile. These are the main contributing factors to the poorer physiological health of low socioeconomic groups. At present, our knowledge of how socioeconomic status and health are related is limited. A necessary step in improving our understanding of this issue is to draw together all the empirical evidence and use it as the basis for developing a theory of socioeconomic health inequalities. We present a conceptual framework to facilitate this process.