Multiple sclerosis (MS) is a chronic but incurable disease of the central nervous system (CNS) that is often diagnosed in the second or third decade of life. It is more common among women than men, significantly impairs patient quality of life, and is associated with substantial costs to patients, healthcare systems, and society. Of the approximately 2.3 million individuals worldwide that have MS, more than 400,000 reside in the United States. Although the etiology of MS is not completely understood, a great deal of evidence suggests a complex relationship between environmental and genetic factors. The pathophysiology of MS involves an aberrant attack by the host immune system on oligodendrocytes, which synthesize and maintain myelin sheaths in the CNS. There are 4 identified disease courses in MS, and approximately 85% of people with MS present with relapsing-remitting MS, which is characterized by discrete acute attacks followed by periods of remission. Signs and symptoms of MS are dependent on the demyelinated area(s) of the CNS and often involve sensory disturbances, limb weakness, fatigue, and increased body temperature. The criteria for a diagnosis of MS include evidence of damage in at least 2 separate areas of the CNS, evidence that the damage occurred at different time points, and the ruling out of other possible diagnoses. Diseasemodifying drugs (DMDs) that reduce the frequency of relapses, development of brain lesions, and progression of disability are the standard of care for relapsing forms of MS, and the use of DMDs should be initiated as early as possible.