To describe the epidemiology of children under age 3 diagnosed with central nervous system tumors in Canada. Case ascertainment: Retrospective observation study of children under age 3 diagnosed with neoplasm involving the central nervous system between 1990 and 2005 at 13 of the Canadian pediatric oncology centres. Results: Case ascertainment was 573 persons. Below 6 months of age at diagnosis, no gender difference was seen and the commonest location of tumor was supratentorial. Embryonal tumors were the commonest, increased head circumference and vomiting were the commonest presenting symptom and survival rates were poor. Over 6 months of age at diagnosis, male predominance occurred and commonest location of tumor was the cerebellum. The commonest tumor was astrocytic, vomiting was the commonest presenting symptom and survival was better than in the under 6-month age group. Conclusion: Over the study period, the incidence rate and degree of resection remained stable. A trend to increased survival in children with ependymal tumors occurred; while, with medulloblastoma, survival decreased.