Endometrial carcinoma is the most common malignancy of the female genital tract. Although it is often thought of as a single disease, there is epidemiological and clinicopathological evidence to support the view that it encompasses two broad categories of malignant epithelial tumors. Each broad category is composed predominantly of one histological type of endometrial carcinoma. The most common is uterine endometrioid carcinoma (UEC) and the other less common, but more aggressive type, is called uterine serous carcinoma (USC). We are currently using molecular approaches to define the differences, and the similarities, in the molecular genetic alterations of the two types of endometrial carcinoma and develop a genetic mouse model of endometrial tumorigenesis.