Background: There is an enduring association between socioeconomic position and health, both over time and across major causes of death. Children and adults with intellectual disabilities are disproportionately represented among the poorer and less healthy sections of the population. But research on health inequalities, and on the broader societal influences on health, has yet to be integrated into perspectives and policy for people with intellectual disabilities. Methods: The paper reviews evidence on the patterns and causes of socioeconomic inequalities in health. Results: It points to evidence that socioeconomic position is the fundamental determinant of health, drawing on longitudinal studies to highlight how it exerts its influence on health from before birth and across the lifecourse. The factors shaping an individual's socioeconomic position are also discussed. Conclusions: The paper concludes by identifying research and policy challenges.