Prognostic studies were performed on 17 cases with clear cell carcinoma of the ovary. The results are follows: 1) The average age was 45.9 years and ranging from 35 to 57 years. 2) Regarding the FIGO clinical stage, all of 5 patients with stage I and 3 of 5 with stage II survived over 2 years, while all of patients with stage III and 2 with stage IV were dead within 2 years. 3) Of 9 patients who had complete resection for primary operation, 8 (89%) survived over 2 years. All of 8 patients who had incomplete resection were dead within 2 years. 4) All cases had been received various chemotherapy; CQ + 5-FU (n = 5), CPM + ADM + CDDP + 5-FU (n = 7), 5-FU + CPM + MMC (n = 2), CDDP (n = 1), CDDP + MMC + 5-FU (n = 1), MCNU + VCR + 5-FU (n = 1), but none of them improved the prognosis of this histological type. 5) With or without administration of CDDP, there was no significant difference in the prognosis. These results suggest that early diagnosis of disease, curative surgical resection and selection of effective chemotherapeutic agents are important things to improve prognosis of clear cell carcinoma of the ovary.