An 81-year-old woman, diagnosed as having a lower bile duct carcinoma by percutaneous transhepatic cholangiography and cytology of the bile after the onset of repeated nausea and fever around November, 1986, was given a pancreatoduodenectomy in February, 1987. From histological analyses of specimens taken at surgery, papillary adenocarcinoma of the lower bile duct was revealed with a massive amount of mucin in the cancerous gland lumens, the bile duct and the tubular adenocarcinoma retained in the mucosal layers of the gallbladder. Lying between these carcinoma sites was found atypical epithelia of a lesion borderline between benign and malignant (Group III). The patient's postoperative progress was fair, but she died suddenly of cerebral hemorrhage in July, 1988. No intraperitoneal or general carcinoma relapse was found at autopsy. This is one of the relatively rare cases of a simultaneous development of gallbladder and bile duct carcinomas and we found it of great interest that these carcinomas existed through an intermediate atypical epithelium.