The objective of this study was to determine the prevalence and incidence of the most frequent chronic health problems in relation to age in people with intellectual disabilities living in residential facilities in the Netherlands. A prospective cohort study was done with four data collections, each with an interval of one year. Data were collected by means of questionnaires which were completed by each person's physician. Striking results included the reported high prevalence and incidence of visual and hearing impairment, which was even more pronounced in people with Down's syndrome than in people with intellectual disability resulting from other causes. Gastrointestinal problems also appeared to have high incidence rates. Dementia was frequently reported in people with Down's syndrome aged 40 years and older. The results reflect the need for a more predictive policy which can anticipate health problems in people with intellectual disability.