In order to control pain during the early postoperative period, patient-controlled analgesia (PCA) with buprenorphine as an analgesic drug was applied in 23 patients undergoing abdominal operations. With this "on demand" system, the patient was allowed to self administer narcotic analgesic medication using a programmable infusion pump. Overdose could be minimized with a mandatory lock-out interval between allowable injections. Average total requirement of buprenorphine was 0.355 mg at 48 hr after operation. Nineteen of the 23 (82.6%) patients characterized their pain control as "excellent" or "good". In these patients there existed high correlation between the total number of patient attempts and the number of successful injections. The PCA system was thought to provide improved pain relief at smaller total drug dosages. In addition, earlier and greater spontaneous physical activity was maintained with PCA therapy. The potential for overdose could be minimized, and thereby PCA appears to be an efficacious and safe method of providing for postoperative pain relief, patient-controlled analgesia ; postoperative pain ; buprenorphine ; abdominal surgery Patient, controlled analgesia (PCA) allows patients to self-administer small doses of analgesic medications as necessary to control postoperative pain. Although the concept of PCA therapy is not new (Forrest et al. 1970; KeeriSzanto 1971;Sechzer 1971), recent progress in the area of infusion pump technology has renewed interest in this concept. PCA equipment consists of an infusion pump electronically connected to a timing device. The patient triggers the device by depressing a thumb button conveniently located on a cord extending from the machine.The objective of this study was to evaluate the efficacy of the Bard Harvard PCA system (White 1985) using buprenorphine as an analgesic drug for providing postoperative pain relief.