The operative results of hilar carcinoma of the bile duct are extremely poor and there are few long term survivors. During the past seven years and six months at our clinic, 26 of 32 patients with hilar carcinoma were operated upon and 24 of these patients underwent resection with a resectability rate of 92.3 per cent. There was one operative death and the mortality was 3.8 per cent in 26 patients operated upon and 4.2 per cent in 24 patients who underwent resection. Seven are still alive postoperatively. The longest survival time is five years and seven months without a recurrence after right trisegmentectomy for carcinoma of the intrahepatic bile duct with hilar invasion. Curative resection was performed upon ten of 26 patients who underwent operation. Of the patients who were operated upon, 12 had invasion of the parenchyma of the liver at the hilum and 11, invasion of the caudate lobe, including direct invasion in three and invasion of the bile ducts in eight. Therefore, the caudate lobe should be resected for radical operation for hilar carcinoma. In this study, the anatomy of the hilar area, including vascular structures of the caudate lobe, was evaluated in 106 cadavers, concerning radical operation for hilar carcinoma.