Interpleural analgesia improves pulmonary function after cholecystectomy. The purpose of this study was to examine the effects of interpleural bupivacaine on analgesia and ventilatory capacity after cholecystectomy. Forty-two patients undergoing elective cholecystectomy were randomly assigned to two groups: one to receive interpleural administration of bupivacaine-adrenaline mixture (Group 1 = 22 patients) and the other standard administration of intramuscular meperidine (Group 2 = 20 patients) for postoperative pain relief. The intensity of pain was evaluated by a visual analogue scale (VAS) preoperatively as well as at 2, 8, 24 and 48 hr postoperatively. At the same time, FVC and FEV1.0 measurements were obtained for all patients. The group given interpleural bupivacaine had better pain relief with mean VAS of 0.6 +/- 0.9 (mean +/- SD) 1.1 +/- 1.4, 0.6 +/- 0.9 and 0.8 +/- 1.2 compared with 5.2 +/- 2.2, 5.8 +/- 2.7, 5.5 +/- 2.2 and 4.5 +/- 1.8 for patients receiving meperidine (P less than 0.001). The patients in Group 1 also had larger FVC and FEV than those in Group 2: FVC 22 +/- 14.5 per cent vs 32 +/- 15.2 per cent (P less than 0.005), FEV1.0 25 +/- 15.5 vs 38 +/- 14.8 per cent (P less than 0.001) (mean +/- SD). We conclude that the interpleural analgesia can achieve better pain relief with greater ventilatory capacity than a standard analgesic regimen in the first two days after cholecystectomy. 