A new cell line, designated TMCC-2, has been established from operation material from a woman with endometrial clear cell carcinoma. TMCC-2 was successively subcultured 40 times in about 1 year. The monolayer culture cell showed a pavement-like arrangement of polygonal and short spindle-shaped cells, and had a tendency to pile-up without contact inhibition. Since PAS positive and Alcian-Blue negative substance could be seen in the cytoplasm, the cells were found to produce glycogen. The population doubling time, the saturation density and plating efficiency of the 25th passage cells were 24 hours, 1.8 x 10(5) and 23%, respectively. The nuclear DNA histogram obtained by flow cytometry showed two peaks at 2.1C and 4.1C. Therefore, the DNA index was 1.05. A tumor maker assay of the culture medium revealed significantly high values for TPA, CA125, CA19-9, and SLX compared with the control medium. The TMCC-2 cells produced the tumors in nude mice after subcutaneous transplantation. In addition, the histological findings were similar to those in the original tumor. As mentioned above, the TMCC-2 cell line derived from endometrial clear cell carcinoma will be very valuable in basic research on clear cell carcinoma of the endometrium.