The aim of this study was to assess mobility impairment and morbidity and mortality caused by internal conditions and cancer in an ageing population with mild to severe intellectual disability. Seventy subjects with a mean age of 70 years (range 60-92 years) at initial evaluation, were assessed during a 10-year prospective longitudinal study. As was to be expected, there was a high prevalence of mobility impairment (30% under and 58% over age 75), similar to reports from other ageing populations with intellectual disability, and of related conditions (chronic constipation, pulmonary function loss and urinary incontinence). Overall morbidity and mortality caused by internal disease and cancer might be comparable to that in the general ageing Dutch population, but questions concerning the specific contribution of risk factors will have to be addressed. The lack of or atypical presentation of subjective symptoms was striking. Nevertheless, autopsy outcomes showed that diagnosis in people with intellectual disability can be as accurate as in the general population, if performed actively.