Background: The aim of this study was to evaluate theexpression of Bcl-2 and Ki-67 in tamoxifen (TAM)-associatedendometrial polyps and postmenopausal polyps.Material and Methods: For this purpose, a retrospectiveanalysis of paraffin-embedded specimens was carriedout. Polyps of 20 postmenopausal and 14 TAM-treatedpatients, 11 simple endometrial hyperplasia, 10 atypicalcomplex endometrial hyperplasia and 8 endometrial adenocarcinomaspecimens were included in the study.Hematoxylin/eosin-stained sections were evaluated. Immunohistochemicalstaining was performed to investigatethe expression of Bcl-2 protein and the Ki-67 proliferationindex. Results: There was no statistically significantdifference between the 5 groups with regard to Bcl-2 staining (p > 0.05). However, Bcl-2 expression inTAM-associated polyps was higher (86%) than in thepostmenopausal control group (80%). Positive Ki-67 washighest in the endometrial adenocarcinoma specimens,followed by the atypical complex endometrial hyperplasiagroup (p < 0.0001). Compared to these 2 groups, Ki-67 expression was lower in TAM-associated polyps, butKi-67 indexes were significantly higher in the TAM-associatedgroup than in the control group (p < 0.0001). Conclusion:Since TAM-associated polyps tend to have higherproliferation indexes and Ki-67 ratios than controlgroups, we suggest that they are likely to have a highermalignant potential.