Buprenorphine is a low molecular weight, lipophilic, opioid analgesic. Recently, a transdermal matrix patch formulation of buprenorphine has become available in three dosage strengths designed to release buprenorphine at 35, 52.5 and 70 micro g/h over a 72-hour period. At least satisfactory analgesia with minimal requirement for rescue medication (</=0.2 mg/day sublingual buprenorphine) was achieved by 34-50% of patients with chronic pain treated with transdermal buprenorphine 35, 52.5 or 70 micro g/h and 31% of placebo recipients, in one double-blind, placebo-controlled, randomised trial. In one trial involving patients unsuccessfully treated with weak opioids or morphine, 36.6% and 47.5% of buprenorphine 35 micro g/h and 52.5 micro g/h recipients, respectively, experienced at least satisfactory analgesia and received </=0.2 mg/day of sublingual buprenorphine compared with 16.2% of placebo recipients (both p </= 0.032). The requirement for rescue medication was reduced from baseline in >50% of patients treated with transdermal buprenorphine, in two trials. Furthermore, despite the availability of rescue medication to all patients, those receiving transdermal buprenorphine tended to experience greater pain relief, reduced pain intensity and longer pain-free sleep. Transdermal buprenorphine was generally well tolerated. Systemic adverse events were typical of opioid treatment or were attributable to the underlying disease.