This article, aimed toward the nonneurologist specialist, presents current indications for MRI in the CNS. Primary and metastatic brain tumors, white matter disease, stroke and hemorrhage, hydrocephalus, and spinal disease are discussed. Emphasis is placed on the contribution of MRI to the evaluation of these major classes of disease. Because of its improved sensitivity and noninvasiveness, in most instances MRI is the initial imaging procedure of choice in the CNS.