A moderately-differentiated endometrial adenocarcinoma cell line(EI) was established from a surgical specimens obtained from a 55-year-old woman with endometrial carcinoma. This cell line could be transplanted to nude mice, where the cells showed the same histological type as the primary tumor. The doubling time of the cell line was 50.5 hours; the saturation density was 7.5 x 104 cells/cm2; the plating efficiency was 46%. This cell line was determined to produce TPA, but not other tumor markers, such as CA125 or CEA. Neither estrogen receptor, nor progesterone receptor was detected from the culture cell or the primary tumor. Chromosome analysis revealed that cells examined were all 46,XX, + 8,t(14q14q), and only cells with this karyotype were thought to be able to grow. From these results, it was suggested that a gene on No. 8 chromosome would be involved in the carcinogenesis of endometrial adenocarcinoma. Thus this cell line was thought to be useful for the clarification of gene conversion during the process of development of endometrial adenocarcinoma.