Objectives: Poly (ADP-ribose) polymerase (PARP-1) is involved in the processes of DNA repair, contributing to the maintenance of genomic stability. Recent data suggest that polymerase is involved in the development of endometrial adenocarcinomas and more advanced tumors displaying lowest enzyme protein expression. Data on PARP-1 activity regarding carcinogenesis in human endometrium are scarce. That was the reason why the authors of the present work wished to investigate the enzyme activity in human uterine hormone-dependent cancer and to compare the results with those obtained for normal endometrial tissue. The next aim was to check whether enzyme activity in normal and cancerous endometrium depends on the number of AP sites, which are widely known as oxidative stress DNA damage markers and PARP-1 activity stimulators. Material and methods: Universal Colorimetric PARP Assay Kit was used to estimate the enzyme activity in units/mg protein. Apurinic sites/105 base pairs (bp) were measured by Oxidative DNA Damage Kit Quantitative. Results were calculated for 47 endometrial samples and 15 uterine adenocarcinomas specimens. Finally, the PARP-1 activity was analyzed for histological and some clinical features of neoplasms. Results and conclusions: 1. no differences in PARP-1 activity were found in non-cancerous types of human endometrium; 2. mean enzyme activity was lower in sporadic endometrial cancers than in noncancerous endometrial specimens (2.89±0.55 vs 6.39±0.06; p<0.005); 3. mean PARP-1 activity in lower grade neoplasms was higher than in G3 tumors and was lower in adenocarcinomas displaying deep uterine wall infiltration; 4. there was no relationship between PARP-1 activity and AP level.