Endometrial cancer is the most common gynecologic malignancy in more developed countries. Approximately 75% of cases are diagnosed at an early stage with a tumor confined to the uterine corpus. Although most patients are cured by surgery alone, about 15-20% with no signs of locally advanced or metastatic disease at primary treatment recurs, with limited responsiveness to systemic therapy. The most common basis for determining the risk of recurrent disease has been classification of endometrial cancers into two subtypes. Type I, associated with a good prognosis and endometrioid histology and type II, associated with a poor prognosis and non-endometrioid histology. This review will focus primarily on the molecular biomarkers that have supported the dualistic model of endometrial carcinoma and help determine which patients would benefit from either adjuvant therapy or more aggressive primary treatment.