Since the establishment of extraovarian peritoneal serous papillary carcinoma (EPSPC) as a clinical entity in 1959, less than 250 cases have been described and its clinicopathologic features remain obscure. The present series is a retrospective, case-controlled study comparing the response and survival to cytoreductive surgery followed by cisplatin-based multiagent chemotherapy of 33 women with confirmed EPSPC versus 33 cases with papillary serous ovarian cancer (PSOC). Each EPSPC case was matched to a PSOC control for extent and distribution of disease prior to and following cytoreductive surgery, tumor grade, patient age, and treatment. Additionally, the new Gynecologic Oncology Group criteria for the diagnosis for EPSPC are discussed. There were no significant differences in tumor response to therapy, disease-free interval, and actuarial survival between cases and controls. These data suggest that EPSPC is clinically similar to PSOC and support the need for a prospective clinical trial to compare these two entities further.