The most frequent solid tumors in the pediatric age group are central nervous system tumors. Despite dramatic improvements in neurosurgery, radiotherapy and chemotherapy, the overall prognosis remains poor, and is often associated with late deleterious effects, including neuropsychologic disorders, endocrine deficiencies and physical abnormalities. In part I, we describe the common presenting symptoms and signs in children with brain tumors. We expose the significant advances in histology, immunohistochemistry, cytogenetic, radiology and therapeutic approaches during the past ten years.