Between 1978 and 1989, gallbladder cancer was diagnosed in 17 out of 48 patients with anomalous union of the pancreaticobiliary system. The clinical, surgical, and pathological features of these 17 patients are described. We classified them into two groups, those with and those without dilation of the common bile duct, and compared the clinicopathological features. Patients with dilation of the bile duct often had early onset of symptoms, so that cancer was detected at a relatively early stage. Most of those without dilation of the common bile duct already had a number of severe symptoms at the first consultation, and the cancer was usually at an advanced stage. We believe that early diagnosis of patients without dilation of the bile duct is an important clinical problem that needs to be resolved.