PURPOSE: Laparoscopic cholecystectomy (LC) has replaced open cholecystectomy (OC) for the majority of patients. However, a minority of patients still require conversion to open cholecystectomy during the perioperative period. This study was designed to determine the contributing factors related to conversion to open cholecystectomy. METHODS: The data from 3,510 laparoscopic cholecystectomies, performed at Chung-Ang university hospital from September 1990 to June 2001, were reviewed retrospectively. Pre-operative laboratory data, post-operative pathologic findings, complications, and the reasons for conversion to open cholecystectomy were evaluated. RESULTS: Sixty six (1.88%) of 3,510 patients were converted to open surgery, due to bleeding (39%), adhesion (26%), bile duct injury (23%) and inflammation (6%). These conversion cases were more prevalent in males and needed longer hospital stay. Thickening of the gallbladder wall and gangrenous cholecystitis were frequent pathologic findings among the conversion cases. CONCLUSION: Thickening of the gallbladder wall, inflammation and anatomical variation of the gallbladder were important factors for conversion to open surgery. Thus, these predictive findings allow the surgeons to preoperatively discuss the higher risk of conversion and allow for an earlier judgement and decision on conversion if intraoperative difficulty is encountered.