Background: Patients with metastatic or recurrent CC who are not amenable to curative treatment with surgery or radiation have a poor prognosis, and systemic chemotherapy is regarded as a standard treatment. Based on the JCOG0505, we considered tri-weekly cTC as the standard regimen. We subsequently focused on dose-dense, weekly administered paclitaxel, which was more effective than conventional administration for breast cancer and, in Japan, ovarian cancer. The efficacy and safety of ddTC have not been evaluated for CC. Therefore, we designed JCOG1311 to confirm the superiority of ddTC to cTC in metastatic or recurrent CC. However, Bmab was approved in Japan for treatment of metastatic or recurrent CC on May 2016. We amended the protocol to add the criteria by which patients would receive Bmab. Methods: Major eligibility criteria are stage IVB, persistent, or recurrent CC patients including SCC or adenocarcinoma histology. We enroll patients according to institution, PS, and platinum-free interval as adjustment factors, whether they receive carboplatin (AUC of 5) on day 1 plus either paclitaxel (175 mg/m²) on day 1 (cTC), or paclitaxel (80 mg/m²) on day 1, 8, 15 (ddTC). Both treatments are repeated every 3 weeks. They can receive Bmab (15 mg/kg) every 3 weeks if not contraindicated. 14 of planned 56 with measurable lesion receiving Bmab in phase II part, of which the primary endpoint is response rate (RR), have been enrolled until January 2018. If the RR of ddTC + Bmab arm is greater than that of cTC + Bmab arm plus 5%, the study will proceed to phase III part, which has OS as the primary endpoint. We hypothesize that the 2-year OS of ddTC arm will be greater than that of the cTC arm (i.e., ≥ 45% compared to 35%). According to the Schoenfeld and Richter method, the required sample size is total 420 patients, with one-sided α of 0.05 and β of 0.20 during 3.5 years of accrual and 2 years of follow-up. This trial is supported by the Japan Agency for Medical Research and Development. And, this trial was registered at the UMIN Clinical Trials Registry as UMIN000019191. Clinical trial information: 000019191.