The clinical and pathologic features and long-term follow-up of eight patients with biliary cystadenoma and six patients with biliary cystadenocarcinoma are reported and the previous literature is reviewed. All the cystadenomas were in middle-aged women, but the six cystadenocarcinomas occurred in both male (4) and female (2) patients. The majority of the patients with cystadenoma and half of those with cystadenocarcinoma presented with an abdominal mass. Four of the patients whose cystadenoma was excised are alive and well for periods of time ranging from 2 % to 13 years. Two of the patients with cystadenocarcinoma have survived for three years a n d for three years a n d eight months, respectively, after subtotal hepatic lobectomy. Morphologically the cystadenocarcinomas differ from the cystadenomas in that the former have cellular pleomorphism and anaplasia and infiltration of the underlying fribrous stroma; they can invade adjacent viscera and may occasionally metastasize to distant sites. The presence of benign epithelium in most cystadenocarcinomas supports their origin from cystadenoma.