A phase III study of carboplatin vs cisplatin in CAP regimen for ovarian cancer was conducted by a cooperative study group consisting of 22 institutions nationwide. The response rate for 23 cases allocated to carboplatin regimen group was 34.8% and 42.1% for 19 cases allocated to cisplatin regimen group. No significant difference was observed between these two regimens in response rates, and no significant differences were noted between the two regimens in each of the clinical toxicities and abnormalities in laboratory findings. Since the carboplatin regimen group did not require hydration, or the use diuretics or antiemetics, these results suggested that carboplatin is more useful in the treatment of ovarian cancer than cisplatin.