Magnetic resonance cholangiopancreatography (MRCP), when performed with heavily T2-weighted fast spin-echo sequences and a phased-array torso coil, provides high-resolution images of the biliary tree and pancreatic duct in multiple planes of section. Use of maximum-intensity projection (MIP) reformations is helpful when overall three-dimensional views are needed (eg, in cases of cholangiocarcinoma), but the source image must be carefully compared with the MIP reformation to avoid missing potential filling defects and other important details obscured by the reformation. Preliminary work indicates that the accuracy of MRCP is comparable to that of endoscopic retrograde cholangiopancreatography in diagnosing the cause of bile duct obstruction. At MRCP, bile duct stones appear as hypointense foci within high-signal-intensity ducts, and stones as small as 2 mm in diameter can be seen. In cases of cholangiocarcinoma, the main advantage of MRCP is that it can noninvasively provide a three-dimensional overview of the biliary tree, which can help in planning treatment. However, the limited spatial resolution of MRCP curtails its role in the characterization of bile duct stenosis, visualization of small intraampullary tumors, and diagnosis of chronic pancreatitis. MRCP is an important adjunct to traditional pulse sequences in the work-up of pancreatic and biliary diseases.