An examination of the primary and secondary diagnoses of 1195 defendants admitted to an urban forensic service was carried out. This indicated that personality disorders dominated the referral patterns from the court. Of those conditions which could produce thought disorders, schizophrenia dominated. An analysis of the prevalence of schizophrenia among defendants charged with homicide in St. Louis revealed a rate of schizophrenia similar to that found in the general population. Organic brain syndromes resulted in a large proportion of assaultive behavior, and these cases also involved a large number of secondary diagnoses. Alcohol and drug abuse were the most common secondary diagnoses. In general, no correlation between psychiatric diagnosis and types of criminal activity was found.