Buprenorphine has been studied extensively since 1978 when it was initially proposed as an alternative to methadone for treatment of opioid dependence. Early work by Jasinski et al., 1978; Mello and Mendelson, 1980; Mello et al., 1982; Mello et al., 1983 and Mendelson et al., 1984 and their colleagues demonstrated buprenorphine's low physical abuse potential and its ability to substitute for heroin and reduce heroin self-administration in opiate-dependent humans. The subsequent early clinical studies suggested that, in clinical settings, buprenorphine was a safe and efficacious opiate dependence pharmacotherapy. Formal approval for general clinical use, however, required that systematic data be gathered on buprenorphine's safety and efficacy in larger groups and a series of controlled clinical trials was designed to evaluate its utility from a medication development perspective. In general, these trials adhered to one of three basic protocol designs: comparison of buprenorphine to methadone; dose comparisons using dose response as an indicator of efficacy; and comparison of buprenorphine to placebo. Retention in treatment, reduction in illicit drug use and craving, and patient and staff ratings of improvements were the most frequently used outcome indicators in these trials. Additional data collected included optimum dosing and dosage schedules, adverse reactions and common side-effects, and other information intended to clarify buprenorphine's benefit-risk relationship and to help prepare guidelines for its safe marketing and utilization by physicians in general clinical practice. This paper presents a review of the buprenorphine/methadone comparison trials conducted in the United States and two such trials conducted in Europe. Also reviewed are three placebo-controlled trials and a buprenorphine/methadone detoxification study. Overall, this series of studies did firmly establish the efficacy of buprenorphine alone and in comparison to methadone.