Background: The role of HIPEC for recurrent EOC is not well defined. The aim of this phase II study was to determine the proportion of pts without evidence of disease progression at 24 months post SCS +/- intraoperative carboplatin HIPEC. Methods: After SCS to ≤ 0.5 cm residual visible disease pts were intraoperatively randomized to carboplatin HIPEC (800mg/m² for 90 minutes) or no HIPEC. The HIPEC arm received 5 additional and the standard arm received 6 postoperative cycles of IV platinum-based chemotherapy without maintenance treatment. Based on an exact binomial single stage “pick the winner” design, each arm is considered “winner” if ≥ 17/49 pts are without evidence of disease progression at 24 months post SCS. Secondary objectives include postoperative grade ≥ 3 toxicity and complications within 4 weeks post SCS, and pharmacokinetics of carboplatin HIPEC. Results: Of 98 pts, 49 (50%) were randomized to the HIPEC arm. The arms were well balanced for age, stage, histology, BRCA mutation status, prior chemotherapy, and disease-free interval. Complete gross SCS was achieved in 94% of the standard and 82% of the HIPEC arm (p = 0.12). Bowel resection was performed more frequently in the standard (65%) compared to the HIPEC arm (37%; p = 0.008). Median operative time was shorter in the standard (296 minutes) compared to the HIPEC arm (475 minutes; p < 0.001). There was no perioperative mortality and no difference in use of ostomies, length of stay or postoperative toxicity. At a median follow-up of 27.7 months (range: 8.8-81.8 months) 70 of 98 pts progressed and 26 died with a median progression free survival (PFS) of 14.3 months (12.1-16 months) and a median overall survival (OS) of 55.2 months (47.7-not reached). At 24 months post SCS 32 pts progressed within 24 months in the standard versus 35 in the HIPEC arm. There was no statistically significant difference in median PFS (15.4 vs 12.3 months, p = 0.173) or median OS (69.2 vs 53.1 months, p = 0.317) between arms. These are preliminary efficacy estimates as 83/98 pts have a minimum of 24 months follow-up. Conclusions: The HIPEC arm did not reach the predefined “winner” endpoint; the standard arm is still undetermined as 6 pts did not reach 24 months follow-up. No perioperative mortality, and no increased perioperative morbidity or toxicity was seen with HIPEC. SCS with carboplatin HIPEC followed by 5 cycles of platinum-based chemotherapy was not superior to SCS without HIPEC followed by 6 cycles of platinum-based chemotherapy. Clinical trial information: NCT01767675