BACKGROUND Pentazocine is one of the most popular analgesics for postoperative analgesia in Japan. For patient-controlled analgesia (PCA), however, opioid agonists are used commonly, and little information is available concerning PCA by pentazocine. We studied the effects of postoperative PCA using intravenous pentazocine. METHODS Eighteen male patients who had undergone open reduction and internal fixation of fructure of extremities under general anesthesia received intravenous pentazocine via PCA. The procedure of PCA was as follows; continuous infusion set 1.5-2.5 mg x h(-1), size of bolus set 5-10 mg with 10-15 minutes lockout interval. We added droperidol for prevention of nausea and vomiting. RESULTS Eleven patients (61.1%) recovered without using any other analgesics. However, seven patients needed other treatments. Six patients used suppository of diclofenac and the other one received pentazocine intramuscularly besides diclofenac. Four of seven patients received these additional analgesics without PCA bolus. No significant complications were observed except nausea in three patients, drowsiness in two and somnolence in one. CONCLUSIONS Our program of PCA was safe and effective for postoperative analgesia. But the guidance for patients, surgeons and nursing staff is important using PCA therapy more effectively.