A retrospective review of 388 patients who presented to the Mayo Clinic for treatment of endometrial carcinoma between 1979 and 1983 was performed and the surgical and pathologic observations were documented. An uncommon histologic subtype was detected in 52 patients (13%): 20 adenosquamous, 14 serous papillary, 11 clear cell, 7 undifferentiated. In contrast to the survival of patients with endometrioid lesions (92%), the overall survival in these patients was only 33%. Each of the individual abnormal histologic subtypes exhibited a survival of less than 50%. At the time of surgical staging, 62% of patients with unfavorable histologic subtypes had extrauterine spread of disease. Despite liberal utilization of postoperative adjuvant therapy in 42 of the 52 patients (81%), only 10% of these patients survived 5 years. Fifty-five percent had a component of recurrence outside of the abdominal/pelvic cavity. Subsequent treatment considerations should incorporate regimens addressing systemic and local tissue control.