An epithelial cell line designated FPCK-1 has been established from a tubular adenoma developing in a male familial polyposis coli (FPC) patient. The FPCK-1 cells grow very slowly with abundant mucus production and have been maintained stably for 3 years in culture. No growth was evident either in soft agar or nude mice. FPCK-1 cells present a normal male karyotype and do not show loss of specific loci on chromosomes 5, 17, 18, and 22 which have been reported to be lost frequently in human colon carcinomas. The cells have neither a point mutation on codon 12 of K-ras gene nor gene amplification of myc, c-H-ras, and/or c-K-ras genes. These results thus suggest the existence of hitherto unknown causative event(s) underlying adenoma development in FPC patients. The FPCK-1 cell line should prove useful for further analytical investigation of the multiple steps involved in human colon carcinogenesis.