Cytogenetic studies of human endometrial carcinomas were performed using a tissue culture technique. Seventeen cases or 40.5% of 42 trials for culture could be analyzed. The mode of chromosome number was found at the diploid range in all cases, and the exact counting of the modal range revealed that the peak of the number was 46 in 75% of the analyzed cases. The distributions were even in the hypo- and hyper-diploid areas. The karyotype analyses showed that the majority of endometrial carcinomas presented pseudodiploid chromosomes, revealing irregular numerical alterations of each group constitution and scattered variant chromosomes with minor structural changes. Only 4 cases had an unclassified chromosome with marked structural aberrations. A marker chromosome was identified in only 1 case, whereas no common specific chromosome was noted and the histologic findings did not correlate with chromosome aberration. From this tissue culture study, carcinomas of human corpus uteri consist of cells with pseudodiploid chromosomal constitution. A culture method would be a desirable procedure for the cytogenetic study.