Four of the patients were excluded because they did not meet the criteria for abuse or dependency. Subjects were administered the Oakdale Diagnostic Interview, which is a structured interview that addresses substance abuse, depression, anorexia, and antisocial personality disorder. Subjects also completed a psychosis questionnaire from the Minnesota Multiphasic Personality Inventory and a questionnaire on substance use family history. The family history portion required the subjects to indicate their family history of substance abuse by relative and type of substance used. Only parents or siblings were considered. All nonalcoholic substance abuse was considered in one category because of subjects' questionable knowledge of family members' specific type of substance abuse and for ease of interpretation in log linear modeling. Family history data revealed 180 subjects (60 percent) with a positive first degree family history of alcohol abuse and 92 subjects (31 percent) with a positive first degree family history of drug abuse. Results clearly support familial transmission of substance abuse; however the reason for such transmission cannot be inferred from the data. The transmission is probably influenced by a complex interaction of multiple genetic and environmental variables. 3 tables, 2 figures, 15 references.