Objective.Ovarian germ cell tumors (GCT) show greater histologic and biologic heterogeneity than their testicular counterparts and remain poorly understood. Ploidy analysis was performed on ovarian GCT registered on Pediatric Oncology Group germ cell tumor protocols 9048 and 9049 to distinguish biologically distinct subsets of immature teratomas and malignant ovarian germ cell tumors.