Research into the health of people with intellectual disabilities has increasingly focused on the occurrence of cancer in this population. Information on the incidence and prevalence of cancer is reviewed in both institutional and community settings. Examples of environmental causation are considered including "Helicobacter pylori." Gender-specific issues are considered with respect to both women and men, and screening services discussed. The overall issue of timely diagnosis of cancer in members of this population is reviewed with special reference to avoidable deaths. The need for methodologically sound studies to clarify the epidemiology of cancer in people with intellectual disabilities is discussed.