• We investigated the prevalence of DSM-III disorders in 792 children aged 11 years from the general population and found an overall prevalence of disorder of 17.6% with a sex ratio (boys-girls) of 1.7:1. The most prevalent disorders were attention deficit, oppositional, and separation anxiety disorders, and the least prevalent were depression and social phobia. Conduct disorder, overanxious disorder, and simple phobia had intermediate prevalences. Pervasive disorders, reported by more than one source, had an overall prevalence of 7.3%. Examination of background behavioral data disclosed that children identified at 11 years as having multiple disorders had a history of behavior problems since 5 years of age on parent and teacher reports. Fifty-five percent of the disorders occurred in combination with one or more other disorders, and 45% as a single disorder.