Eighty-five patients, 52 with endometrioid carcinoma (EC), nine with mixed endometrioid and clear cell carcinoma (MC), and 24 with clear cell carcinoma (CC), were studied to determine if prognosis was affected by (a) mixed tumor histology, (b) grade of the endometrioid component in ECs, and MCs, (c) presence of benign or malignant squamous differentiation in ECs, (d) solid versus tubular histology in CCs, (e) endometriosis in the same ovary as the tumor or elsewhere in the pelvis, (f) tumor stage, (g) patient age, or (h) presence of a coexisting carcinoma of the endometrium. The 5 year survivals for the ECs, MCs, and CCs were 52%, 22%, and 69%, respectively, for all stages. The 5 year survivals for Stage I ECs and CCs were 82% and 93%, respectively. None of these differences were statistically significant. Higher stages of disease for all three tumor types and higher grades of the endometrioid component of the ECs and the MCs were associated with significantly decreased survival. Patients with CCs had a significantly increased incidence of pelvic endometriosis (67%) versus patients with ECs (17%) or MCs (22%) (p less than 0.001). Survival was not significantly affected by benign or malignant squamous differentiation in ECs, tubular differentiation in CCs, patient age, the presence of endometriosis, or a coexisting carcinoma of the endometrium.