Endometrial carcinoma is one of the most common cancers in women, with an incidence of 2.6%. This chapter examines the effects of the woman's hormonal environment on the development of endometrial hyperplasia and endometrial carcinoma, additional risk factors, and preventive measures for this common malignancy. When hormonetherapy consisted of unopposed estrogen, a higher incidence of endometrial hyperplasia and carcinoma was found in women on this therapy compared with non-treated women. A systematic review of randomized controlled trials found unopposed estrogen therapy in moderate to high doses to be associated with significant increases in rates of endometrial hyperplasia. The risk of endometrial carcinoma in complex atypical hyperplasia is approximately 25%, and warrants surgical management with hysterectomy and salpingoophorectomy. The accuracy of endometrial biopsy as compared with dilation and curettage in detection of endometrial carcinoma ranges from 91 to 99.6% with sampling devices such as the Pipelle.