Sclerosing adenocarcinoma of the extrahepatic bile duct and pyometra were diagnosed in a 17-year-old entire female Siamese cat which had had anorexia, depression, acute icterus and abdominal distension for about a week. Clinical signs derived from he tumor were minimal and non-specific until the diffuse thickening of the bile duct obstructed bile flow and acute icterus resulted. Sclerosing adenocarcinoma of the extrahepatic bile duct is a human variant of bile duct carcinomas that has not, to the authors' knowledge, previously been described in the cat, but it appears to be as invasive as other feline hepatic tumours.