PURPOSE: A study was performed to compare the detectability of extrahepatic duct stones between nonenhanced and enhanced computed tomography(CT). MATERIALS AND METHODS: Consecutive 30 patients with extrahepatic duct stones were analyzed with special attention to the detectability of stones between nonenhanced and enhanced CT. The extrahepatic duct was further divided into two segments, one above(suprapancereatic) and the other in(intrapancreatic) the head of the pancreas. Conspicuity of the stone was graded as "visible", "suspicious", and "invisible". Three radiologists reviewed the CT images without prior information and determined the location of stone and grade of their conspicuity. RESULTS: The stones were located at the suprapancreatic common duct in 5 patients, intrapancreatic common duct, in 15 patients and both portion of the duct in 10 patients. There was no difference in the detection rate of stones between the two images at suprapancreatic common duct, and was 93%, However, the rate at intrapancreatic common duct was 95% and 64% on nonenhanced and enhanced CT scans, respectively. The overall detection rate was 95% on nOnenhance CT and 75% on enhanced CT. CONCLUSION: We concluded that nonenhanced CT was prerequisite to evaluate the extrahepatic duct stones in addition to enhanced CT.