In a histopathologic review of 1985 cases of endometrial carcinoma 97 patients (4.9%) had clear cell carcinoma (CCC). Mean age at diagnosis was 65.3 years. The crude 5- and 10-year survivals for all stages were 42.3 and 30.9%, respectively. Fifty-nine percent of the patients in surgicopathological stage I and 27% in stage II survived 5 years. Myometrial infiltration and vessel invasion were important prognosticators. Ninety percent of the patients with intramucosal tumors survived 5 years, in contrast to only 15% of the patients with deep myometrial infiltration. Seventeen percent of the patients with vessel invasion survived 5 years, in contrast to 49% of the patients without this finding. CCC is one of the most aggressive subtypes of endometrial carcinoma.