Background: The objective of this study is to evaluate the safety and efficacy of adding bevacizumab to dose-dense adjuvant chemotherapy with bevacizumab maintenance after neoadjuvant chemotherapy (NAC) and interval debulking surgery (IDS) for stage III/IV ovarian, tubal, and primary peritoneal cancer. Methods:This phase II clinical trial using Simon's minimax two-stage design was conducted. At the first stage, 13 subjects were enrolled, and the trial would proceed to second stage if ≤3 subjects discontinued treatment for study-defined significant adverse events (AEs). Patients with stage III/IV ovarian, tubal, and primary peritoneal cancer deemed not feasible for primary cytoreductive surgery were enrolled after 3 to 4 cycles of NAC and IDS without disease progression. NAC could be either weekly paclitaxel (80mg/m²) (dose-dense) plus 3-weekly carboplatin (AUC5-6) or 3-weekly conventional schedule. After IDS, postoperative dose-dense adjuvant chemotherapy for 3 cycles at least (best to 6 cycles), and 3-weekly bevacizumab 15mg/kg was given since postoperative cycle 2. Further 3-weekly maintenance bevacizumab 15mg/kg was given intravenously for 17 cycles. Results: Of the 22 enrolled subjects, 13 (59.1%) had no gross lesion after IDS. Of the 13 subjects enrolled on the 1st stage, one study-defined significant AE occurred, therefore the trial proceeded to the 2nd stage (n = 9). The median progression-free survival (PFS) was 22.1 months (95% confidence interval [CI], 13.7 – 30.5), and the median overall survival (OS) was 49.2 months (95% CI, 33.8 – 64.6). Peritoneal Cancer Index score at entering abdomen during IDS was significant for PFS (>12 vs ≤ 12: p = 0.003). One of the 22 subjects did not receive any study treatment. In the safety analysis (n = 21), grade 3/4 AEs included thrombocytopenia of 38.1%, neutropenia 71.4%, and anemia 28.6%. Study-defined significant AEs of bowel perforation, poor-healing wound, and hypertension were found in 1 case each, respectively. Conclusions: This phase II trial demonstrated adding bevacizumab to dose-dense adjuvant chemotherapy with bevacizumab maintenance after NAC was feasible with tolerable toxicity and comparable PFS/OS as compared to other studies using bevacizumab in the NAC phase or dose-dense scheduling throughout. Clinical trial information: NCT02022917