A human cell line (KMCH-1) derived from a surgical specimen of combined hepatocellular and cholangiocarcinoma has been established. The original tumor consisted of both hepatocellular carcinoma of the trabecular type and cholangiocellular carcinoma. This cell line has been maintained for 26 months through 75 passages. KMCH-1 cells show characteristics of adenocarcinoma on light and electron microscopy. They proliferate in culture in a pave stone arrangement. The doubling time of these cells at the 24th passage was 39 hr. Chromosome analysis revealed a chromosome number ranging from 60 to 98, with a modal number of 74. KMCH-1 cells produced tumors several months after subcutaneous and intraperitoneal transplantations into athymic nude mice. Histologically, the subcutaneous tumors were poorly differentiated adrenocarcinoma, while intraperitoneal tumors were moderately to well-differentiated adenocarcinoma. Hepatocellular carcinoma components were not observed. Thus, KMCH-1 cells demonstrate the feature of cholangiocellular carcinoma in vitro and in vivo. This KMCH-1 cell line is the first established combined hepatocellular and cholangiocarcinoma cell line and may contribute to further investigation of combined hepatocellular and cholangiocarcinoma.