Aim. The first Swedish National Guidelines for Ovarian Cancer (NGOC) were published in 2012. We aimed to evaluate surgical outcomes and survival in patients with stage IIIC-IV disease, before and after the NGOC implementation. Method. Women with primary epithelial ovarian cancer, FIGO stage IIIC?IV, registered in the Swedish Quality Registry for Gynecologic Cancer 2008?2011 and 2013?2016 were included. Surgical outcomes were analyzed, including frequency of complete cytoreduction (R0). Relative survival (RS) and excess mortality rate ratios (EMRRs) were computed as measures of survival. Univariable and multivariable regression (Poisson) were calculated. Results. In total, 3728 women were identified, 1746 before and 1982 after NGOC. After adjusting for age and stage, survival was improved 2013?2016 vs. 2008?2011 (EMRR 0.89; 95%CI:0.82?0.96, p < 0.05). For women undergoing primary debulking surgery (PDS), R0 frequency (28.9% vs. 53.3%; p < 0.001) and 5-year RS (29.6% (95% CI:26.8?32.8) vs. 37.4% (95%CI:33.6?41.7)) were increased, but fewer patients (58% vs. 44%, p < 0.001) underwent PDS after NGOC implementation. Median survival for the PDS cohort increased from 35 months (95%CI,32.8?39.2) to 43 months (95%CI,40.9?46.4). In the neoadjuvant chemotherapy (NACT) + interval debulking surgery (IDS) cohort, R0 increased (36.8% to 50.1%, p < 0.001), but not 5-year RS (17.5% vs. 20.7%,ns). Compared to PDS, the EMRR was 1.32 (95%CI,1.19 & ndash;1.47, p < 0.001) for NACT+IDS and 3.00 (95% CI,2.66 & ndash;3.38, p < 0.001) for chemotherapy alone. In multivariable analyses, PDS, R0, age <= 70 years, and stage IIIC were found to be independent factors for improved RS. Conclusion. Implementation of the first National Guidelines for Ovarian Cancer improved relative survival in advanced ovarian cancer. (c) 2021 Published by Elsevier Inc.