A human carcinoembryonic antigen-producing colon carcinoma cell line has been established. The cells form acinar structures and signet ring cells. The lumen of the acini presents microvilli and a glycocalyx. Neighboring cells show desmosomes and terminal bars. The cells present an aneuploid karyotype with a modal number of 49. No marker chromosomes are found, although a significant proportion of cells show an altered A2 chromosome and an extra B. Exponentially growing cultures produce 54 ng of carcinoembryonic antigen/10(6) cells. Kinetic parameters are as follows: doubling time, 37 hr; mitotic index, 0.8%; labeling index, 31%; generation time, 30 hr; G1 phase, 7 hr; S phase, 18 hr; G2 phase, 5 hr; growth fraction 90%. This cell line, designated line LoVo, represents an in vitro model for human colon carcinoma.