An assessment has been made, with the cooperation of 22 institutes, of 1,185 cases of ovarian cancer as subjects who were treated in the period from January, 1980, to December, 1987. As a result, (1) As for distribution by clinical staging at the initial examination, the cases in Stage III were the most numerous, followed by those in Stage I, and if classified according to the histological type, serous cystadenocarcinoma was the most frequently observed in Stage III, and undifferentiated and unclassified carcinomata were observed in Stages III and IV. (2) In the examination of prognostic factors, it was confirmed that the clinical stage, histological type and diameter of the remaining tumor after the initial operation were important factors. (3) A significant difference was observed between the grade of histomorphological differentiation and prognosis, the difference was chiefly due to the deviated distribution of clinical staging in each group of differentiation. (4) A favorable trend was observed in the prognosis by patient's age toward the younger layer. (5) When the starting time of the therapy is considered, a trend toward improvement has been seen year by year, and it is considered that the beneficial effect of chemotherapy with CDDP contributes to this.