This study analyzes the mortality, hospitalizations, and arrests in a cohort of severe intravenous heroin users divided into three groups: those in methadone treatment, those discharged from treatment, and those who never received treatment. The study population consists of 101 heroin users, of whom 56 were HIV-seropositive. Because of intensive drug misuse, they underwent coercive residential treatment in Stockholm during the 3-year period 1986-1988. The mortality was lower in the methadone group, and all seven deaths were related to HIV-infection. Outside the program, 24 of 29 persons died from external violence and poisoning.