A novel macaque cell line (J3K) with epithelial phenotypes was spontaneously established from a kidney specimen of a Japanese macaque (Macaca fuscata). Its population doubling level reached more than 500, and it was regarded as an established permanent cell line. J3K cells have transformed cell phenotypes such as loss of contact inhibition and anchorage-independent cell growth. Unlike other monkey adherent cell lines, J3K had no SV40 large T antigen. After establishment, cells have constantly expressed telomerase activity, whereas telomere length has been maintained. No mutations in the coding regions of the p53 complementary deoxyribonucleic acid were detected in the late-passaged cells. J3K, a novel transformed epithelial cell line, will be useful material for the comparative study of human and other primate cellular aging as well as cancer cell biology.