The category of germ cell tumors includes a broad array of histologic subtypes ranging from the benign, mature teratoma to the primitive, aggressive embryonal carcinoma (Box 1). These tumors share their origin in a primordial germ cell with multipotent capacity for differentiation along a variety of pathways. Several theories have been proposed to explain the origin and location of these tumors. Some investigators support the theory of aberrant migration of primitive germ cells originating in the embryonic yolk sac [1,2]. An alternative theory is that these tumors arise from totipotent cells originating in the primitive knot and primitive streak that invaginate between the layers of the bilaminar disc to form the mesoderm [3]. Germ cell tumors tend to occur in the midline or para-axial locations of the body. Sacrococcygeal tumors are the most common, followed by gonadal, mediastinal, retroperitoneal, and multiple other rare sites. Germ cell tumors may also occur in the brain but are not included in this review. Germ cell tumors are seen at all ages in childhood, with different age peaks for the various anatomic sites. In any given tumor, there may be a mixture of the various benign and malignant subtypes of germ cell histologies. Two of the malignant cell types secrete proteins that may be detected in the systemic circulation. Endodermal sinus tumors secrete alpha fetoprotein (AFP) and choriocarcinomas secrete beta human chorionic gonadotropin (bHCG). The development of sensitive assays for these tumor markers has improved diagnostic accuracy and monitoring of therapy for these subtypes of malignant germ cell tumors. In the prechemotherapy era, survival of patients who had malignant germ cell tumors treated with surgery alone was rare. The advent of multiagent regimens such as vincristine/dactinomycin/ cyclophosphamide (VAC) resulted in some progress, but the development of platinum-based regimens in the 1980s and 1990s dramatically improved survival. Children who have malignant germ cell tumors currently have