People with intellectual disabilities have poorer health than their non-disabled peers. They are also more likely to be exposed to a wide range of environmental adversities in childhood. Research undertaken in the general population has demonstrated that exposure to environmental adversity in childhood can have an adverse impact on health and well-being across the life course. Recently, research in this area has added new breadth and depth to our understanding of: (1) the extent to which cumulative exposure to environmental adversities across the life course, but especially in early childhood, can reduce health and well-being; (2) the social, psychological and biological mediating pathways through which environmental adversities may impair health; (3) the processes associated with resilience and vulnerability in the face of exposure to adversity; and (4) the social significance of these effects in accounting for the magnitude of the inequalities in health that are apparent both between and within populations. This new knowledge is making a significant contribution to the development of social policies that seek to combine health gain with the reduction in health inequalities. This paper attempts to apply this knowledge to research aimed at understanding and improving the health and well-being of people with intellectual disabilities.