Reports that central nervous system (CNS) cancer rates are increasing have prompted debate on whether secular trends reflect environmental changes related to etiology or artifacts of case ascertainment. We present the most recent data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results program on incidence rates and trends of CNS malignancies, including primary CNS lymphomas, and on survival probability. We discuss the new 2000 standard for adjusting rates; underreporting of CNS tumor rates resulting from the exclusion of nonmalignancies in most cancer registries; and information on CNS tumor risk factors, including concerns related to nonionizing electromagnetic fields and wireless mobile telephones.