Through the collaboration of 22 institutions nationwide, a total of 1,185 cases of ovarian cancer treated between January, 1980 and December, 1987, were investigated as to their prognosis from the aspect of the chemotherapeutic effect. (1) An excellent effect of the remission-induction chemotherapy was observed in a group receiving combination therapy with CDDP as the main ingredient. In particular a significant effect was seen in stages III and IV. In addition, the effect on the remaining tumors by diameter also showed a significant difference in cases of tumors of not less than 2 cm in diameter. (2) As to the effect on histological types, a comparison in stage III showed a favourable effect on endometroid, serous and mucinous adenocarcinomas, while no effect was observed in clear cell adenocarcinoma. (3) The effect of the remission induction chemotherapy did not always give rise to an improvement in the long-term prognosis of ovarian cancer, and the establishment of a therapeutic method aimed at the prevention of recurrence was desired. (4) To improve the long-term prognosis, intermittent (or cyclic) chemotherapy with CDDP as the main ingredient was found to be very effective, but maintenance chemotherapy with orally administered of 5-Fluorouracil or Tegaful was not effective. (5) The effect of the conventional immunotherapy was not observed at all.