The case histories and radiologic studies of eight liver transplant recipients who developed a mucocele of the allograft cystic duct remnant were retrospectively evaluated. All patients had clinical and/or laboratory evidence of biliary obstruction or cholangitis from 2 weeks to 3.3 years following transplantation. Cholangiographic, ultrasound (US), and computed tomography (CT) images were available for review in eight, five, and four patients, respectively. Cholangiograms demonstrated an extrinsic mass compressing the common hepatic duct in seven of eight patients. US and CT showed fairly well- to well-defined round fluid collections adjacent to the common hepatic duct in three and two patients, respectively. The findings of this study suggest that the detection at cholangiography of an extrinsic mass compressing the common hepatic duct appears to be specific for a mucocele of the allograft cystic duct remnant. CT and US images may offer confirmatory evidence.