BACKGROUND Although laparoscopic cholecystectomy has replaced open cholecystectomy for the majority of patients, it is clear that a substantial minority will require laparotomy for safe and successful removal of the gallbladder. METHODS Seven hundred forty-six laparoscopic cholecystectomies performed at LAC+USC Medical Center for January 1991 to May 1993 were retrospectively reviewed. Hospital stay, laboratory values, and complications, as well as the need for and reason for conversion to open cholecystectomy were recorded. There were 661 females and 85 males, with a mean age of 38 years (range 15 to 92). RESULTS One hundred one (14%) of the 746 patients were converted to open cholecystectomy. Difficult dissection secondary to inflammation or adhesions and the need to treat common-bile-duct stones were the most common reasons for conversion. Patients requiring conversion to open cholecystectomy were more likely to have been admitted through the emergency department (72% versus 46%, P < 0.0001), have had prolonged hospital stays prior to surgery (mean time from admission to surgery 4.4 days versus 2.8 days, P < 0.0001), and to have had a thickened gallbladder wall on preoperative ultrasound (54% versus 20%, P < 0.001). CONCLUSIONS The most common reasons for conversion to open cholecystectomy are inflammation and adhesions secondary to severe acute and chronic disease and/or the need for clearance of the common bile duct. Patients who were admitted to the emergency department, particularly if they were managed nonoperatively for a period of time and had a preoperative diagnosis of acute cholecystitis, were more likely to require conversion to open cholecystectomy.