Until recently, disability was presumed to be equivalent to illness, with similar expectations of dependence, inactivity, and exclusion from participation in community life (Krahn et al., 2006). People with disabilities were reputed to necessarily have poorer health. However, models of disability have evolved to recognize environmental as well as individual impacts on functioning, with a corresponding change in expectations for community participation. The World Health Organization (WHO) defines health as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity" (WHO, 1948). This definition underlies the fundamental premise of this chapter, that having a disability does not ordain poor health, and that good health is an attainable goal for people with intellectual and developmental disabilities (IDD). Health is an important aspect of well-being for everyone. This chapter provides an overview of health issues for children and adults with IDD. While people with IDD can be healthy, they are more vulnerable to health disparities.Health disparities are health differences that adversely affect socially disadvantaged groups (Braveman et al., 2011). Just as there are many causes of IDD, many determinants contribute to what has been termed a "cascade of disparities" in this population (Krahn et al., 2006). These determinants of health include genetic, social circumstance,