The aim of the present study was to investigate the prevalence of behavior problems among people with administratively defined intellectual disability (ID) and identify possible risk markers for behavior problems using the Behavior Problems Inventory (BPI). Sixty-two percent of the ID population (n=915) had a behavior problem (self-injurious, stereotyped, or aggressive/destructive behavior) and 18.7% had a behavior problem identified as challenging behavior, resulting in a prevalence of 80.3 per 100,000 in the base population. The most pronounced risk markers for behavior problems were severity of ID, autism, night sleep disturbances, sensory hypersensitivity, communication dysfunction, social deficits, psychiatry involvement, and psychotropic medication. About 50% of people with behavior problems were on psychotropic drugs. Protective markers were Down's syndrome and, to some extent, cerebral palsy. The results were largely consistent with those reported in previous studies. Findings not previously reported were that prevalence of aggressive/destructive behavior peaked among those =70 years. Highlighting groups within a population at particular risk has implications for management and treatment of individuals with behavior problems.