Putative precursors of endometrial cancer such as complex endometrial hyperplasia with atypia have been described to be monoclonal and considered to be genetically related. In order to identify a genetic marker that could serve as a putative predictor of endometrial cancer we analyzed 14 endometrial hyperplasia and 29 endometrial cancer samples for instabilities and loss of heterozygosity (LOH) in microsatellite sequences. Deletions on the short arm of chromosome 8 were frequently detected in both endometrial hyperplasia and cancer samples, suggesting that these deletions are early events in the development of endometrial cancer.