Elderly people with intellectual disability have high rates of both psychiatric and physical disorders. In the elderly general population, these disorders are known to be associated. Whether such an association exists amongst elderly people with intellectual disability is unclear, but the resolution of this question is of clinical as well as academic importance. Psychiatric and physical assessments were completed on 134 people with intellectual disability aged 65 years and over (93.7% of the ascertained population living in Leicestershire, UK). The relationship between the two disorders was statistically examined. The number of physical disorders, age, level of intellectual disability and smoking status were retained in the logistic regression equation which predicted caseness for dementia in 79.9%. Similar statistical modelling for psychiatric disorders (other than dementia) retained the level of intellectual disability as the only explanatory variable in the equation. These results differ from the elderly general population, but are in keeping with the one previous intellectual disability study. In view of the poor use of general medical services by elderly people with intellectual disability, knowledge of such comorbidity should alert psychiatrists to the need for physical assessments in order to optimize health.