Ultrasonic energy has recently been used for surgical cutting and coagulating. A prospective randomized study was undertaken to determine the effectiveness of ultrasonic energy versus monopolar electrosurgery in human laparoscopic cholecystectomy. Two hundred patients were enrolled and randomized into two groups of 100 patients each. Group A patients underwent laparoscopic cholecystectomy with monopolar electrocautery. Group B patients underwent laparoscopic cholecystectomy with ultrasonically activated shears. In 18 cases of this group, the cystic artery was coagulated and cut without clips. Subhepatic closed drainage was left for 24 h in patients who were candidates for oozing of blood or leakage of bile. The median operating time was 45 min in group A and 37 min in group B. Subhepatic drainage was left in 37 patients of group A and 26 of group B. The median blood loss was 14 ml in group A and 2 ml in group B, while 3 patients of group A and none of group B had bile leakage from the bed of the gallbladder for 1, 1, and 6 days, respectively. Postoperative ultrasound examination showed a minor subhepatic fluid collection in 5 patients of group A and in 1 patient of group B. All these collections were treated without drainage. The length of hospital stay was 1.9 +/- 0.5 days in group A and 1.4 +/- 0.2 days in group B. Postoperative pain scores, nausea, and vomiting were equivalent in both groups. It is concluded that ultrasonically activated coagulating shears are safer, easier to use, faster, and less prone to intraoperative complications and postoperative morbidity than monopolar electrocautery in laparoscopic cholecystectomy.