Tamoxifen is widely used in the breast cancer treatment. Its side effects on the endometrium are well-known, but more and more worse prognosis uterine sarcoma are described. Based on recent literature review, the cause and effect chain between tamoxifen and uterine sarcoma is argued, which confirms that a risk exists as from 2 years of treatment, a cumulative dose of 15 g, and that malignant mixed mesodermal tumours appear to be the most frequent.