After laparoscopic cholecystectomy, residual gas is inevitably retained in the peritoneal cavity. An active attempt is not always made to remove it. Using a double-blind prospective protocol in 40 healthy patients, we evaluated the effect of residual pneumoperitoneum on post-laparoscopic cholecystectomy pain intensity. On completion of surgery, prior to removal of the surgical instruments, the patients were randomly divided into two groups: in the active aspiration (AA) group an active attempt was made to remove as much gas as possible from the peritoneal cavity, while in the nonactive aspiration (NAA) group no such effort was made. Postoperative pain was assessed hourly over a 4-h period with a visual analog scale (VAS) and a patient-controlled analgesia (PCA) device. During the first postoperative hour, the NAA patients made significantly (P < 0.05) more demands (mean +/- SD) for morphine than those in the AA group (31.3 +/- 26.2 vs 15.3 +/- 15.7) and also received a borderline significantly (P = 0.056) larger dose (mean +/- SD) of PCA morphine (3.9 +/- 1.9 mg vs 2.7 +/- 1.3 mg). The VAS scores (mean +/- SD) over the 4-h study period were similar in both groups, being high during the first postoperative hour (AA = 5.1 +/- 2.1 vs NAA = 6.1 +/- 2.2) and then decreasing. We conclude that residual pneumoperitoneum is a contributing factor in the etiology of postoperative pain after laparoscopic cholecystectomy.