Endometrial carcinoma remains the most common invasive gynecologic malignancy. Increased longevity is associated with an increased incidence of endometrial carcinoma (EC) in elderly women. While recent studies have looked at aging and its relation to ovarian, breast, and cervical cancer, few have focused on EC in the growing elderly population. This study analyzed 35 histologic specimens of EC in women 75-92 years of age. Findings revealed that only 23% of the tumors were Stage I, G1. The majority (77%) were deeply invasive or of advanced stage (IC-IV). These were G2, G3, or "virulent" types of nonendometrioid EC (undifferentiated, clear cell, uterine serous papillary, and squamous cell carcinoma). Fifty-seven percent of tumors were endometrioid, of which 9% were mixed, including a rare case of nongestational choriocarcinoma. The nonendometrioid tumors, compared to the endometrioid types, were more often high-stage tumors with vascular invasion. They were also more often associated with atrophic (vs hyperplastic) uninvolved endometrium. Clinical risk factors (nulliparity, obesity, estrogen replacement therapy) were assessed and correlated with the histologic findings. It was shown that tumors in the elderly were less likely to be estrogen-related. It was concluded that EC in this age group is more aggressive, histologically less differentiated, and often nonendometrioid compared with EC in the general population. The increased virulence of EC in the elderly may be related to the tumor's independence from hormonal factors, to the poorly understood but well-known diminished immunologic defense against cancer in general in elderly patients, and/or to the belated diagnosis of the disease in this population.