Anomalous junction of the pancreaticobiliary duct (AJPB) is a rare, congenital anatomic abnormality of the biliary system and is thought to be associated with a high risk of developing carcinoma of the gallbladder. We have had two cases of AJPB-associated gallbladder carcinoma in the past four years. Case 1: a 42-year-old female complaining of right upper quadrant pain was found in an abdominal sonogram to have irregular thickening of the gallbladder wall. Endoscopic retrograde cholangiopancreaticography revealed an abnormally elongated common channel; an abdominal CT scan and celiac angiogram showed a gallbladder tumor with invasion to the liver base. Case 2: a 36-year-old female presented with right upper quadrant pain and a palpable mass. A gallbladder tumor was found in an abdominal sonogram. Intraoperative cholangiography showed an abnormally elongated junction of the pancreaticobiliary duct. In these two cases, adenocarcinoma of the gallbladder was proven by pathology after surgical excision. Since AJPB and bladder carcinoma are both rare, the coexistence of these two diseases indicates that patients with AJPB have a high risk of developing gallbladder carcinoma. It is suggested that patients with AJPB should be closely followed. A prophylactic cholecystectomy may be indicated in some cases because of the high risk of developing gallbladder carcinoma.