Buprenorphine, a powerful opioid, is newly available for delivery in a transdermal formulation. The transdermal system's matrix patch provides rate-controlled administration of the drug. Three double-blind, placebo-controlled trials were conducted to evaluate efficacy and tolerability of the buprenorphine transdermal system (buprenorphine TDS, Transtec). A total of 445 patients were enrolled in the studies. All suffered from moderate to severe and very severe pain, both cancer- or non-cancer-related. The percentage of responders increased as the rate of buprenorphine delivered by the transdermal system rose, ranging from a 29% (cancer) and 36% (non-cancer) response rate associated with the lowest dose (35 microg/h), to 40% (cancer) and 46% (non-cancer) with the highest dose (70 microg/h). Patients receiving buprenorphine TDS slept longer, uninterrupted by pain, than patients from the placebo group. Systemic adverse effects reported in the drug cohorts included nausea, vomiting and dizziness, and were typical of those reported in other studies of opioids; local adverse events, most commonly erythema and pruritus, were transient and mild to moderate. In an open-label, follow-up trial, in which 239 patients from the original clinical studies participated, 90% of patients reported that their analgesia was satisfactory or even better over a mean duration of 4.7 months; nearly 95% of patients found the patch to be user-friendly. The new buprenorphine TDS appears to be an important new modality for administering analgesia in patients with non-acute pain.