To evaluate the degree of intratumoral DNA ploidy heterogeneity in endometrial carcinoma, the authors examined curettage specimens from 30 patients with clinical stage I and II endometrial carcinoma. The curettage material was obtained before the onset of treatment. A representative sample from each tumour was chosen and a 50 microm section was cut. The paraffin block of tumor was then divided into 4 equal parts and a 50 microm section was cut from each part. All tumour samples were analysed separately by flow cytometry. DNA ploidy heterogeneity was noted in 5/29 cases (17%). In three cases DNA-aneuploid stem cell lines were found only among the 4-part sections and were not detected when the whole tumor section was analysed.