This retrospective analysis intends to evaluate by histeroscopy the endometrial findings in a group of 63 patients in post-menopausal treated with tamoxifen for breast cancer. Our patients assumed tamoxifen for a different period between 6 and 120 months. Patients have been divided in two groups: I) patients undergoing hysteroscopy because of some clinical symptoms; II) patients who undergoing hysteroscopy as a routine examination. The most important observation of this work is the correlation between the presence of negative endometrium and low risk hyperplasia (LRH) associated to: symptomatology and duration of therapy. In the group of asymptomatic patients the LRH is found only after 3 years of treatment, while in the group of symptomatic patients, LRH is present within the first two years of treatment; beyond this period high risk hyperplasia (HRH) and endometrial carcinoma have been diagnosed. We also observed a higher incidence of endometrial polyps in this population than among the non treated group and among the symptomatic patients. From these data we conclude that hysteroscopy follow-up has to be performed in the group of patients treated with tamoxifen and that it would be necessary to have a hysteroscopy before the beginning of therapy and that this one has to be repeated once a year through the treatment. Obviously the symptomatic patients have to undergo hysteroscopy as soon as possible as a higher incidence of HRH and endometrial carcinoma has been detected in this group of patients.