Because the outcome of methadone and buprenorphine substitution treatment in adolescents is unclear, we completed a retrospective cohort study of 100 consecutive heroin-dependent adolescents who sought these treatments over an 8-year recruitment period. The participants' average age was 16.6 years, and 54 were female. Half of the patient group remained in treatment for over 1 year. Among those still in treatment at 12 months, 39% demonstrated abstinence from heroin. The final route of departure from the treatment program was via planned detox for 22%, dropout for 32%, and imprisonment for 8%. The remaining 39% were transferred elsewhere for ongoing opiate substitution treatment after a median period of 23 months of treatment. Males were more likely to exit via imprisonment (p b .05), but other outcomes were not predicted by gender. There were no deaths during treatment among these 100 patients who had a cumulative period of 129 person years at risk. Our findings suggest that this treatment delivers reductions in heroin use and that one fifth of patients will exit treatment following detox completion within a 1- to 2-year time frame