BACKGROUND AND AIMS: Although the gold standard for evaluating the extrahepatic bile duct cancer is endoscopic retrograde cholangiopancreatography (ERCP), the procedure is associated with complications such as cholangitis and pancreatitis. In contrast, magnetic resonance cholangiopancreatography (MRCP) is a noninvasive diagnostic modality capable of producing bigh-quality images of the pancreato-biliary tree. The purpose of this study was to examine the diagnostic accuracy of MRCP and the difference hetween the images of MRCP and ERCP, METHODS: We retrospectively analyzed 17 patients who were diagnosed as extrahepatic bile duct cancer between July 1995 and June 1997. All patients underwent ERCP and MRCP. In MRCP, fast spin echo was used in 10 cases and single shot fast spin echo was used in 7 cases. Malignant obstruction was confirmed in 12 patients by surgical findings and in 5 patients by clinical follow-ups and imaging findings. RESULTS: The ERCP and the MRCP showed sensitivities of 100% and 94% for correct level of obstruction, 100% and 88% for causes of obstruction, 47% and 82% for recognition of the upper margin of lesion, 100% and 82% for recognition of the lower margin of lesion, 47% and 100% for visualization of the bile duct proximal to obstruction, and 100% and 93% for visualization of the bile duct distal to obstruction, respectively. CONCLUSIONS: The MRCP has a diagnostic accuracy similar to ERCP and shows excellent images in recognition of upper margin of lesion and visulaization of the duct proximal to obstruction in extrahepatic bile duct cancer. Therefore, it can be used as a primary diagnostic tool before ERCP or in cases that ERCP is incomplete or cannulation of the duct is not possible.