Purpose Platinum-based chemotherapy (PBC) for patients with progressing ovarian cancer (OC) is more effective with a longer time interval from previous platinum treatment (platinum-free interval [PFI]). In 1999, it was hypothesized that prolonging PFI with single-agent non-PBC (NPBC) may offer a strategy to improve overall outcome. MITO-8 aimed to verify this hypothesis commonly used in clinical practice although it has not been prospectively tested. Methods MITO-8 is an open-label, prospective, randomized, superiority trial. Patients with OC who experienced disease progression 6 to 12 months after their last platinum treatment were randomly assigned 1:1 to the experimental sequence of NPBC followed by PBC at subsequent relapse or the standard reverse treatment sequence. Overall survival (OS) was the primary end point. Results Two hundred fifteen patients were enrolled (standard arm [n = 108]; experimental arm [n = 107]). The trial ended before planned because of slow enrollment. PFI was prolonged in the experimental arm (median, 7.8 v 0.01 months). There was no OS benefit in the experimental arm (median, 21.8 v 24.5 months; hazard ratio, 1.38; 95% CI, 0.99 to 1.94; P = .06). Progression-free survival after the sequence was significantly shorter in the experimental arm (median, 12.8 v 16.4 months; hazard ratio, 1.41; 95% CI, 1.04 to 1.92; P = .025). Global quality-of-life change after three cycles was worse in the experimental arm. Slight differences were observed in the incidence of adverse effects. Conclusion MITO-8 supports the recommendation that PBC not be delayed in favor of an NPBC in patients with partially platinum-sensitive OC. PBC should be used as a control arm in future trials of new drugs in this setting.