A discriminant function analysis was performed with data from 409 high-risk heroin addicts at intake into a methadone maintenance treatment program to determine the characteristics of cocaine users. Cocaine users presented a higher-risk profile for human immunodeficiency virus (HIV), engaged in a wider variety of criminal activities, were more likely to be African-American, reported more alcohol use, and showed more signs of psychological disturbance. A second discriminant function analysis determined that crack smokers differed from non-crack cocaine users in ethnicity, alcohol use, criminal activity, needle use, and marital status. Heroin addicts who use cocaine, in particular crack, represent a sub-group at higher risk and in need of targeted treatment planning and monitoring.