Objective To investigate whether neoadjuvant chemotherapy followed by interval debulking surgery is superior to primary debulking surgery in terms of perioperative complications and progression-free survival, in advanced epithelial ovarian, fallopian tube or primary peritoneal cancer patients with high tumor load. Methods Patients with advanced epithelial ovarian, fallopian tube or primary peritoneal cancer (stage IIIC-IV) underwent laparoscopy. Patients with high tumor load assessed by a standardized laparoscopic predictive index were randomly assigned (1:1 ratio) to undergo either primary debulking surgery followed by adjuvant chemotherapy (arm A), or neoadjuvant chemotherapy followed by interval debulking surgery and adjuvant chemotherapy (arm B). Co-primary outcome measures were progression-free survival and post-operative complications; secondary outcomes were overall survival, and quality of life. Survival analyses were performed on an intention-to-treat population. Results 171 patients were randomly assigned to primary debulking surgery (n=84) versus neoadjuvant chemotherapy (n=87). Rates of complete resection (R0) were different between the arms (47.6% in arm A vs 77.0% in arm B; p=0.001). 53 major postoperative complications were registered, mainly distributed in arm A compared with arm B (25.9% vs 7.6%; p=0.0001). All patients were included in the intent-to-treat analysis. With an overall median follow-up of 59 months (95% CI 53 to 64), 142 (83.0%) disease progressions/recurrences and 103 deaths (60.2%) occurred. Median progression-free and overall survival were 15 and 41 months for patients assigned to primary debulking surgery, compared with 14 and 43 months for patients assigned to neoadjuvant chemotherapy, respectively (HR 1.05, 95% CI 0.77 to 1.44, p=0.73; HR 1.12, 95% CI 0.76 to 1.65, p=0.56). Conclusions Neoadjuvant chemotherapy and primary debulking surgery have the same efficacy when used at their maximal possibilities, but the toxicity profile is different.