Typically, intravenous drug users are studied by drawing samples from drug treatment programs, from the criminal justice system, or by outreach into the street community via anthropological or ethnographic methods. Among 1405 subjects recruited through extensive community outreach, 46% reported no history of treatment for drug abuse and 16% said they had not been arrested in the preceding 10 years; 130 (9%) reported neither history. A history of arrest was higher among men and those with a history of: treatment for drug abuse, low educational attainment, having received public assistance, and unemployment. A history of drug treatment was higher among women and those of an older age with a history of: arrest, having received public assistance, and a greater duration and intensity of intravenous drug use. Intravenous drug users who had neither a history of arrest since 1977 nor of drug treatment were more likely to be women and more educated, to have not received public assistance, and to inject less than weekly. These data indicate that characteristics of intravenous drug users differ by history of arrest and treatment, substantiating reports of heterogeneity among intravenous drug users.