Clinical cases of aberrant bile duct experienced at the department for the past 9 years and 4 months were analyzed to elucidate the surgical problems in prevention of intraoperative injury of aberrant bile ducts. The frequency of the diseases was 8 per 976 cases (0.82%) undergoing cholecystectomy. Number of cases and frequency in each type by modified Hisatsugu's classification was as follows; type I:3 cases (38%), III:2 (25%), N:1(13%), and V:2 (25%). There was no relationship between type or diameter of aberrant bile ducts and intraoperative injury. A result that the preoperative diagnostic methods in two injured cases were both DIC suggests the importance of comprehension of forms of the bile ducts with direct cholangiography at preoperation. There was no relationship between the degree of inflammation at Calot's triangle and intraoperative injury, but the operative methods in two injured cases were both mixed cholecystectomy in which normograde cholecystectomy was performed after temporary ligation of the cystic duct. These results suggest that normograde cholecystectomy, including mixed cholecystectomy, is not always a safety method and careful attention at operation is most important to prevent injury of the aberrant bile duct regardless of operative method.