Purpose To investigate whether initial diagnostic laparoscopy can prevent futile primary cytoreductive surgery (PCS) by identifying patients with advanced-stage ovarian cancer in whom . 1 cm of residual disease will be left after PCS. Patients and Methods This multicenter, randomized controlled trial was undertaken within eight gynecologic cancer centers in the Netherlands. Patients with suspected advanced-stage ovarian cancer who qualified for PCS were eligible. Participating patients were randomly assigned to either laparoscopy or PCS. Laparoscopy was used to guide selection of primary treatment: Either primary surgery or neoadjuvant chemotherapy followed by interval surgery. The primary outcome was futile laparotomy, defined as a PCS with residual disease of.1 cm. Primary analyses were performed according to the intention-To-Treat principle. Results Between May 2011 and February 2015, 201 participants were included, of whom 102 were assigned to diagnostic laparoscopy and 99 to primary surgery. In the laparoscopy group, 63 (62%) of 102 patients underwent PCS versus 93 (94%) of 99 patients in the primary surgery group. Futile laparotomy occurred in 10 (10%) of 102 patients in the laparoscopy group versus 39 (39%) of 99 patients in the primary surgery group (relative risk, 0.25; 95% CI, 0.13 to 0.47; P , .001). In the laparoscopy group, three (3%) of 102 patients underwent both primary and interval surgery compared with 28 (28%) of 99 patients in the primary surgery group (P , .001). Conclusion Diagnostic laparoscopy reduced the number of futile laparotomies in patients with suspected advanced-stage ovarian cancer. In women with a plan for PCS, these data suggest that performance of diagnostic laparoscopy first is reasonable and that if cytoreduction to , 1 cm of residual disease seems feasible, to proceed with PCS.