Laparoscopic cholecystectomy first became popular during the late 1980s and now the procedure is consider the standard approach for symptomatic cholecystolithiasis. This study aimed to assess the value of sonography in predicting intraoperative difficulties for patients undergoing laparoscopic cholecystectomy and in identifying indicators for conversion to open cholecystectomy. This prospective clinical trial conducted in the Department of Surgery of Al-Sadir Teaching Hospital, Al-Mousawi private Hospital and Ibn Al-Baitar private Hospital in Basrah, Iraq, between January 2006 and October 2007. Abdominal sonography performed in 100 consecutive patients before laparoscopic cholecystectomy. The surgeon re-verified sonographic findings in the operating room. Out of 100 patients with cholecystolithiasis on sonography, we encountered straightforward laparoscopic cholecystectomy in 72 patients (72%), difficult laparoscopic cholecystectomy in 20 (20%) and the procedure was converted to open cholecystectomy in 8 patients (8%). Forty two patients had sonography revealing gallbladder wall thickness (>4 mm). The accuracy of sonography for cholecystolithiasis was 99%. In conclusion, an accurate preoperative diagnostic sonography is mandatory for planned laparoscopic gallbladder surgery to provide information for the selection of the most appropriate approach and to avoid intraoperative difficulties and surprises. On sonography, gallbladder wall thickening is the most sensitive indicator of technical difficulties during laparoscopic cholecystectomy, such difficulties may require conversion to laparotomy.