Two epithelial cell lines (TE-1 and TE-2) have been established from a well or poorly differentiated human squamous cell carcinoma of the esophagus. TE-1 has been subcultured 120 times during 2 years and 10 months, and TE-2, 50 times for almost 2 years. Cultured cells grew as isolated and piled-up colonies of epithelial cells. The average doubling time of the TE-1 cell line was 60 hr and that of TE-2, 72 hr. Distinctive marker chromosomes and a male karyotype were present in TE-1, but no marker chromosomes were seen in TE-2. Scanning electron microscopic examinations of both TE-1 and TE-2 confirmed the presence of desmosomes and interdigitated microvilli. Transmission electron micrographs of TE-1 showed the presence of abundant cell organelles, and a few organelles were found in the scanty cytoplasm of TE-2. There was a marked difference in the cell organelles between TE-1 and TE-2. Heterotransplantation of the cultured TE-1 and TE-2 cells produced tumors, the histological appearance of which was similar to that of the original ones. The carcinoembryonic antigen level of the medium in the confluent culture of TE-2 was 270 ng/10(6) cells. In the cytoplasm of TE-1 cells the number of paracrystals, which were produced by treatment with vinblastine sulfate, increased by the addition of cholera toxin to the medium.