The present study was designed to investigate whether the administration of antimicrobial agents before laparoscopic cholecystectomy (LC) is more effective for prevention of postoperative infection. During the period from January 1991 to September 2001, 397 patients treated with sulbactam/cefoperazone (SBT/CPZ) for prevention of postoperative infection were studied: 200 patients received SBT/CPZ 1 hr before LC, and 197 patients were not given the preoperative treatment. The positive rate of bacteria in the gallbladder bile in the group receiving preoperative SBT/CPZ was 12.0%, a significant suppression compared with 19.8% in the group without preoperative treatment (P < 0.05). Identification of microorganisms in the bile revealed E. coli and Klebsiella in the preoperative treatment group, which showed a significant suppression (P < 0.05). The mean white blood cell count was significantly lower in the preoperative treatment group (9860/microl) than in the nonpreoperative treatment group (10,520/microl) (P < 0.05). The above results demonstrate that administration of SBT/CPZ before LC suppressed the level of bacteria in the bile, resulting in a significant reduction in complications induced by postoperative infection.