Endometrial polyps are the most common endometrial pathology described in association with Tamoxifen exposure. The aim of this study was to evaluate the malignant potential of endometrial polyps in breast cancer patients receiving Tamoxifen. We analyzed 140 endometrial polyps divided into two groups: 1) 73 endometrial polyps from 57 breast cancer patients receiving Tamoxifen (Nolvadex): T+ endometrial polyps; 2) 67 control endometrial polyps received for analysis in the period January-December 2000. The analysis was performed on archival H&E sections. We found that the rates of endometrial carcinoma and atypical hyperplasia were high in patients treated with Tamoxifen (7.02% vs 2.99% and 17.54% vs 11.94%), but the results did not reach statistical significance (p > 0.05).