This chapter presents the most up-to-date classification of tumors of the nervous system, based on the histological appearance of the neoplasm and also on information derived from cytogenetics and molecular biology, now recognized worldwide as increasingly important for more precise diagnosis, prognosis, and therapeutic guidance. The chapter provides a detailed morphologic description of each major tumor type, with numerous illustrations of macroscopic and microscopic lesions. First we consider primary tumors of the nervous system, including those derived from neuroepithelial tissue (astrocytic, oligodendroglial, ependymal, neuronal, and glioneuronal), pineal tissue, peripheral nerve sheath, and meninges. Next lymphomas, hematopoietic neoplasms, and secondary (metastatic) neoplasms are described.