International collaboration in clinical trials in the field of gynecologic oncology has a long history. The reason for this is that the number of patients with gynecological cancer is halfway small, making it difficult for a single country to expeditiously conduct phase Ⅲ comparative trials to generate evidences. In order to keep up with this trend, we have been participating in trials under a worldwide network, starting with a joint trial with the United States. In this paper, we introduce our experience and the interesting events we have encountered in the course of these trials.