Aims. To evaluate the safety and efficacy of an 8 mg/day sublingual dose of buprenorphine in the maintenance treatment of heroin addicts by comparison with a 1 mg/day dose over a 16-week treatment period. As a secondary objective, outcomes were determined concurrently for patients treated with two other dose levels . Design. Patients were randomized to four dosage groups and treated double-blind . Setting. Twelve outpatient opiate maintenance treatment centers throughout the United States . Participants. Two hundred and thirty-nine women and 497 men who met the DSM-III-R criteria for opioid dependence and were seeking treatment . Intervention. Patients received either 1, 4, 8 or 16 mg/day of buprenorphine and were treated in the usual clinical context, including a 1-hour weekly clinical counseling session . Measurement. Retention in treatment, illicit opioid use as determined by urine toxicology, opioid craving and global ratings by patient and staff. Safety outcome measures were provided by clinical monitoring and by analysis of the reported adverse events . Findings. Outcomes in the 8 mg group were significantly better than in the 1 mg group in all four efficacy domains. No deaths occurred in either group. The 8 mg group did not show an increase in the frequency of adverse events. Most reported adverse effects were those commonly seen in patients treated with opioids . Conclusions. The findings support the safety and efficacy of buprenorphine and suggest that an adequate dose of buprenorphine will be a useful addition to pharmacotherapy.