A clinical and pathologic review of primary intracranial tumors (917 cases in a 62-year period) at The Hospital for Sick Children, Toronto, identified 21 cases with systemic metastases (2.3%). This included 15 cases of medulloblastoma and 1 case each of astrocytoma, meningeal sarcoma, malignant melanoma, ependymoblastoma, teratoma, and endodermal sinus tumor, adding to the pediatric literature of 94 previously reported cases (72 medulloblastoma and 22 cases of other brain tumors). Like adults, children with medulloblastoma tend to develop bone and bone marrow metastases, while those with other brain tumors frequently invade adjacent tissues, and then spread to regional lymph nodes and the lungs. The prognosis is almost uniformly fatal, although prolonged palliation could be achieved with radiation and/or chemotherapy. The pathogenesis of systemic metastases is related to breakage of the blood-brain barrier, whether at surgery, or with tumor invasion into vascular channels, and especially with preoperative systemic-cerebrospinal fluid shunting. Thirteen of 16 patients who developed systemic metastases, including 5 with peritoneal involvement, had ineffective or no millipore filters within their shunts, suggesting their possible prophylactic role against tumor dissemination. A greater understanding of the pathogenesis of systemic metastases may aid the design of future effective preventive measures.