Guided by the literature on alcohol subtypes, cluster analytical solutions ranging from two to five were evaluated for a large (n = 802), ethnically diverse sample of alcoholic in-patients. Personal interview data were collected from in-patients regarding their substance abuse and psychiatric disorder status, risk factors for psychopathology and health outcomes. The data were collected at five alcohol in-patient treatment settings in New York; three settings were in New York City, one in Rochester and one in Buffalo. The sample included 802 participants (481 males and 321 females) with racial/ethnic group diversity (418 blacks, 180 whites, 187 Hispanics, 17 of other ethnic origin). Subjects were assessed with standardized measures of substance abuse and psychiatric disorders, family history of alcoholism, psychopathy, temperament, alcohol expectancies and clinical health variables. Based on internal and external criteria and compatibility with the existing literature, four subtypes were identified: mild course, polydrug, negative affect and chronic/antisocial. On external criteria, the polydrug subtype had the highest rate of family criminality, high-risk sexual behavior and intravenous drug use; the negative affect subtype had the highest rate of childhood sexual abuse, attempted suicide and childhood homelessness; the chronic/antisocial personality (ASP) subtype had the most severe pattern of drinking and antisocial behavior. Findings are discussed with regard to the etiological and clinical utility of the four-subtype formulation, and consistency with recent studies in molecular genetics and pharmacology.