Colonic cancer cell strain KE43 was established from a human colonic cancer diagnosed histologically as a predominantly well differentiated adenocarcinoma with minute foci of poorly differentiated adenocarcinoma. The well differentiated adenocarcinoma cell line was identified as the major morphological picture in xenografts of KE43 and 58 in nude mice, but this changed to poorly differentiated adenocarcinoma in passage 105. Doubling time of this cancer cell line was 22.5 hours in passage 105. The modal numbers of chromosomes were 41 and 76. Cancer cells could be heterotransplanted in 100% of the nude mice. The tumor cells produced and secreted CA19-9, CEA and Laminin into the spent medium. This cell line appears to provide a useful system for studying colonic cancer in vivo and in vitro.