Aims. To evaluate the effectiveness of buprenorphine compared with methadone maintenance therapy in opiate addicts over a treatment period of 24 weeks. Design. Subjects were randomized to receive either buprenorphine or methadone in an open, comparative study. Setting. Subjects were recruited and treated at the drug addiction outpatient clinic at the University of Vienna. Participants. Sixty subjects (19 females and 41 males) who met DSM-IV criteria for opioid dependence and were seeking treatment. Intervention. Subjects received either sublingual buprenorphine (2-mg or 8-mg tablets; maximum daily dose 8 mg) or oral methadone (racemic D -/+ L-methadone; maximum daily dose 80 mg). A stable dose was maintained following the 6-day induction phase. Measurement. Assessment of treatment retention and illicit substance use (opiates, cocaine and benzodiazepines) was made by urinalysis. Findings. The retention rate was significantly better in the methadone maintained group (p< 0.05) but subjects completing the study in the buprenorphine group had significantly lower rates of illicit opiate consumption (p = 0.04). Conclusion. The results support the superiority of methadone with respect to retention rate. However, they also confirm previous reports of buprenorphine use as an alternative in maintenance therapy for opiate addiction, suggesting that a specific subgroup may be benefiting from buprenorphine. This is the first comparative trial to use sublingual buprenorphine tablets: previously published comparison studies refer to 30% solutions of buprenorphine in alcohol.