The DNA content was investigated by means of flow cytometry in frozen tumor specimens from 33 patients with uterine endometrial carcinoma. The association was tested between ploidy and S-phase fraction on one hand and clinico-pathological parameters on the other. Aneuploidy appeared in 15 (45%) of the patients, and the average S-phase fraction was 0.18 (0.04-0.34). There was a highly significant correlation between DNA-Index (DI) and histologic differentiation (p = 0.01) and a less significant correlation between DI and estrogen receptor content (p = 0.04). DNA ploidy measured by flow cytometry is a highly reproducible parameter that in addition to routine histopathological examination may provide useful information. Further studies are needed to establish the prognostic importance of the flow cytometric parameters.