Case studies of African American youth with conduct disorder were examined in the context of a descriptive evaluation of co-occurring substance-related problems and mental disorders. The purpose of this study was to extend the findings of the Epidemiologic Catchment Area (ECA) study of the National Institute of Mental Health into the area of comorbid assaultive violence and to evaluate recommendations made by J. D. Yoder and A. S. Kahn (1993) for noncomparative and descriptive research designs. Case records of 257 male youth offenders, aged 12-17 years, were reviewed. Variables were documented alcohol- or drug-related problems, referrals or counseling for emotional problems, and incidents of interpersonal violence. Half of these participants had at least one prior offense, and 14% were adjudicated for drug-related offenses not related to alcohol. Thirty-three percent had a history of violent crime. Subjects with an alcohol problem were 18 times more likely to have a co-occurring drug problem, 10 times more likely to have a co-occurring drug-related or mental health problem, and 5 times more likely to have an emotional problem than subjects without a history of alcohol-related difficulties. However, there was no indication of comorbidity of any of these disorders with assaultive violence. Substance-related and mental disorders may share some common pathways, but the mechanisms underlying interpersonal violence appear to be different. (Contains 32 references.) (SLD)