PURPOSE: In SOLO1, maintenance olaparib (300 mg twice daily) significantly improved progression-free survival (PFS) for patients with newly diagnosed BRCA1- and/or BRCA2-mutated advanced ovarian cancer compared with placebo (hazard ratio [HR], 0.30; 95% CI, 0.23 to 0.41; median not reached v 13.8 months). We investigated PFS in SOLO1 for subgroups of patients based on preselected baseline factors. PATIENTS AND METHODS: Investigator-assessed PFS subgroup analyses of SOLO1 included clinical response after platinum-based chemotherapy (complete [CR] or partial response [PR]), surgery type (upfront or interval surgery), disease status after surgery (residual or no gross residual disease), and BRCA mutation status ( BRCA1 or BRCA2). Additionally, we evaluated PFS in patients with stage III disease who underwent upfront surgery and had no gross residual disease. We also report objective response rate. RESULTS: The risk of disease progression or death was reduced with olaparib compared with placebo by 69% (HR, 0.31; 95% CI, 0.21 to 0.46) and 63% (HR, 0.37; 95% CI, 0.24 to 0.58) in patients undergoing upfront or interval surgery; 56% (HR, 0.44; 95% CI, 0.25 to 0.77) and 67% (HR, 0.33; 95% CI, 0.23 to 0.46) in patients with residual or no residual disease after surgery; 66% (HR, 0.34; 95% CI, 0.24 to 0.47) and 69% in women with clinical CR or PR at baseline (HR, 0.31; 95% CI, 0.18 to 0.52); and 59% (HR, 0.41; 95% CI, 0.30 to 0.56) and 80% (HR 0.20; 95% CI, 0.10 to 0.37) in patients with a BRCA1 or BRCA2 mutation, respectively. CONCLUSION: Patients with newly diagnosed advanced ovarian cancer achieve substantial benefit from maintenance olaparib treatment regardless of baseline surgery outcome, response to chemotherapy, or BRCA mutation type.