Surgery and radiation therapy have been the main types of treatment for gynecologic cancer. However, chemotherapy in gynecologic oncology has recently made dramatic progress and presently is becoming the most widespread treatment. After the discovery of cisplatin in the field of chemotherapy for epithelial ovarian cancer, it has now become the leading treatment modality. According to the result of several important phase III randomized control trials (RCTs), the platinum-taxane combined therapy has now become the standard treatment regimen. Regarding endometrial cancer, Cisplatin-Adriamycin-Cyclophosphamide (CAP) therapy has been used as an effective adjuvant chemotherapy in Japan. The adjuvant chemotherapy (Adriamycin-Cisplatin therapy) for the endometrial cancer has now been recognized worldwide as the standard therapy based on the findings of a phase III RCT. Concurrent chemoradiotherapy for cervical cancer has also been recommended as the standard therapy in Japan since 1999 based on the successful results of numerous RCTs which proved its efficacy. The chemotherapy for gynecologic cancers has been investigated and standardized based on the results of numerous clinical trials. These trials have been conducted by many clinical trial groups, such as the Gynecologic Oncology Group (GOG), Southwest Oncology Group (SWOG), and the European Organization for Research and Treatment of Cancer (EORTC) throughout the world, in addition to the Japan Clinical Oncology Group (JCOG) and the Japanese Gynecologic Oncology Group (JGOG) in Japan. The valuable contributions of these clinical trials are helping in the development of new drug therapies, thus leading to such treatment regimens playing increasingly important and wider roles in the field of gynecologic oncology treatment in the future.