Persons with major mental disorders (MMDs) with co-morbid SUDs are at increased risk of homicide. However, there are no published data from clinical interviews or lifetime objective documents on the prevalence of lifetime PD or SUD in a composite sample of psychopathic homicidal offenders. The present study assessed a national sample of men with MMD who had homicidal behavior or attempts (n = 90) using the study’s DSM-IV Axis I and Axis II disorder stereotype clinical interview. Seventy-eight percent of psychotic homicides were diagnosed with schizophrenia, 17% with schizoaffective disorder, and 5% with other psychiatric disorders. 74% had lifelong SUD, 72% had alcohol use disorder. 51% had PD, 47% of which were APD. all those diagnosed with PD had SUD, and only 25% had both SUD and alcohol use disorder. Of those with a dual diagnosis (MMD and SUD), about two-thirds had either PD or APD. these results suggest that two-thirds of psychotic homicide offenders have a dual diagnosis classification: about half have three diagnoses (APD + SUD + MMD), and one-quarter have a “pure” diagnosis. “A fourth classification, “APD + MMD but no SUD,” was not seen. There is no fourth classification – “APD + MMD without SUD”. Severe violence is common in those with MMD, so we need to treat effectively those with a previous APD and a dual diagnosis.