Cholangiocarcinoma is the leading cause of cholestasis among patients with malignant tumors, 63.5 per cent, while carcinoma of the head of the pancreas is the most common cause in western countries. A clinical history of progressive cholestasis; signs and symptoms of cholestasis; slow progressive clinical course, and mostly importantly, 96.7 per cent stemming from an endemic area of opisthorchiasis are all shown in this study. The peak age for this disease in Thailand was about one decade younger than that in western countries. The anatomic lesions in 96.7 per cent were found in the hilar area of the liver and only 3.3 per cent in the lower third of the liver compared with a significant number of lesions in the middle and lower thirds of the liver, as reported in literature from the western countries. We believe that percutaneous transhepatic cholangiography prior to the operation will definitely help the surgeon in deciding upon the surgical approach. Surgical intervention of a cholangiocarcinomatous lesion is probably more difficult in Thailand than in western countries because of location. The incidence for cholangiocarcinoma associated with biliary calculi and for an opisthorchiatic cyst is 8.1 and 6.1 per cent. We would like to emphasize the close association between cholangiocarcinoma and the combination of opisthorchiasis with carcinogenic agents, such as nitrosamines in the favorite local dish. The animal experimental model, using Syrian golden hamsters, produced the same result and the same site for the lesion--the hilar area of the liver.