Efficient use of operating time has become a key concern. The aim of this study was to determine preoperative factors that can predict extended duration of operating time (>90 min) for laparoscopic cholecystectomy (LC).Data collected prospectively on 827 consecutive patients who underwent elective LC between 1990 and 1997 were analyzed. Factors evaluated included age, gender; body mass index; comorbidity; duration of symptoms; history of jaundice, pancreatitis, or abdominal surgery; dilated common bile duct or thick-walled gallbladder on ultrasound; preoperative endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic sphincterotomy (ES); and surgeon experience. Univariate and multivariate analyses were performed to identify factors predicting a long operation.Operating time was longer than 90 min in 276 patients (33%). Predictors of extended operation time were age older than 55 years (odds ratio [OR] = 9.7), preoperative ES (OR = 2.8), and a thick-walled gallbladder on ultrasound (OR = 2.5).These predictors may be useful in planning theater lists and anesthesia management, and in selecting patients for day surgery.