We clinicopathologically reviewed cases of clear cell adenocarcinoma (CCA) of the endometrium and adenocarcinoma of the endometrial type mixed with a clear cell component (AMC). 1. Among 1,152 cases of endometrial carcinoma, CCA and AMC were found in 16 (1.4%) and 21 (1.8%) cases, respectively. 2. As revealed by cumulative survival rates based on the Kaplan-Meier method, the prognosis was significantly poorer in CCA and AMC than in endometrial carcinoma (p < 0.001). 3. As for the subtype of CCA, 5 (31%), 9 (56%) and 2 (13%) cases were papillary, solid, and tubulocystic, respectively. 4. The frequency of epithelial hyaline body, bizarre nucleus, psammoma body, necrosis, lymphoplasmacytic infiltration, lymphatic invasion, vessel invasion, and atypical hyperplasia among cases of CCA was 8 (50%), 7 (44%), 5 (31%), 6 (38%), 8 (50%), 5 (36%), 4 (29%) and 1 (7%) cases, respectively. Histologically, lymphoplasmacytic response was the most closely correlated with the prognosis. 5. Among the cases of AMC, there were 6 cases of metastasis and recurrence. In 5 (83%) of these, the clear component increased markedly in metastatic and recurrent lesions although the component was very minor in the primary lesions.