Prognostic risk factors were statistically analyzed from the histopathologic data obtained from 90 Japanese women with stages I and II endometrial carcinoma treated surgically, including systemic retroperitoneal lymph node dissection, between June 1979 and June 1989. In stage Ia endometrial carcinoma, pelvic and paraaortic nodes metastasis were seen in 13.8(4/29)% and 0.0(0/19)% of patients, respectively. In stage Ib, the incidence of pelvic and paraaortic node metastasis was 25.6(11/43)% and 9.7(3/31)%, respectively. In stage II, the incidence was 38.9(7/18)% and 13.3(2/15)%, respectively. Prognosis of patients even with deep myometrial invasion (greater than or equal to 2/3) or G3 tumor was fairly good (5-year survival rate: 87.5% and 85.7%, respectively) if the disease was histologically confined to the uterine corpus. Once the tumor spread outside the corpus uteri, the survival rate of patients was strongly affected by the grade of the tumor, moderate to marked lymph-vascular space invasion of tumor cells, or tumor invading middle or outer third of myometrium (P less than 0.05 for each factor). In summary, endometrial cancer frequently metastasize to pelvic and paraaortic lymph nodes even in the early stages, and lymph node metastasis and other extracorporeal spread of disease have a serious impact on patient survival. Prognosis of patients with extracorporeal spread of disease seems to be determined by the high grade of tumor and lymph-vascular space invasion. These results suggest that surgical exploration including paraaortic lymph node dissection to accurately evaluate the extent of the disease is essential to estimate the patient's prognostic risk and to individualize the treatment schedule.