Multiple sclerosis, an idiopathic inflammatory disease of the central nervous system, is characterized pathologically by demyelination and subsequent axonal degeneration. The disease commonly presents in young adults and affects twice as many women as men. Common presenting symptoms include numbness, weakness, visual impairment, loss of balance, dizziness, urinary bladder urgency, fatigue, and depression. The diagnosis of multiple sclerosis should be made by a physician with experience in identifying the disease. Diagnosis should be based on objective evidence of two or more neurologic signs that are localized to the brain or spinal cord and are disseminated in time and space (i.e., occur in different parts of the central nervous system at least three months apart). Magnetic resonance imaging with gadolinium contrast, especially during or following a first attack, can be helpful in providing evidence of lesions in other parts of the brain and spinal cord. A second magnetic resonance scan may be useful at least three months after the initial attack to identify new lesions and provide evidence of dissemination over time. It is critical to exclude other diseases that can mimic multiple sclerosis, including vascular disease, spinal cord compression, vitamin B12 deficiency, central nervous system infection (e.g., Lyme disease, syphilis), and other inflammatory conditions (e.g., sarcoidosis, systemic lupus erythematosus, Sjögren's syndrome). Symptom-specific drugs can relieve spasticity, bladder dysfunction, depression, and fatigue. Five disease-modifying treatments for multiple sclerosis have been approved by the U.S. Food and Drug Administration. These treatments are partially effective in reducing exacerbations and may slow progression of disability.