The aim of this study was to assess the efficacy of 1-, 2-, and 4-mg-per-day sublingual doses of buprenorphine in the maintenance treatment of heroin-dependent patients over a 17-week treatment period. Subjects were randomized to three dosage groups. Participants consisted of 105 heroin addicts (102 men and 3 women) who met the DSM-IV criteria for opioid dependence and were seeking treatment. Subjects received buprenorphine at a dose of 1, 2, or 4 mg per day and were treated in an urban outpatient clinic, including a weekly 1-hour individual counseling session. Days retained in treatment were measured. Overall, 49 patients (46.7%) completed the 17-week study. Completion rates by dosage group were 34.3% for the 1 mg dose group, 42.9% for the 2 mg dose group, and 62.9% for the 4 mg dose group. Retention in the 4 mg dose group was significantly better than in the 1 mg dose group (P = .017). None of the other comparisons was significant. The results support the efficacy and safety of buprenorphine for outpatient treatment of heroin dependence and seem to indicate that the highest dose (4 mg) of buprenorphine was the best of the three doses for Iranian heroin addicts to increase their retention in treatment.