Multiple sclerosis (MS) is a chronic, often debilitating disease of the central nervous system (CNS) that affects between 400,000 and 570,000 persons in the United States, with an incidence among females 2 to 3 times that of males. The cause of MS is currently unknown, but immediate family history, low blood levels of vitamin D, and cigarette smoking, among other factors, appear to increase the risk of developing MS. MS is considered an immune-mediated disease, whereby immune cells target and attack the CNS, predominantly the axonal membrane known as the myelin sheath. Depending on which areas of the brain or spinal cord are affected, this can result in a variety of waxing and waning neurologic symptoms. Most patients will eventually suffer from progressive disability that can greatly impact their quality of life. Symptoms such as fatigue, difficulty with ambulation, and depression are common among patients with MS and can affect their ability to work and care for themselves. Costs due to treatment and lost productivity place a significant economic burden on patients, caregivers, families, and society. Current and future treatments may help limit the personal and societal costs of MS by delaying disability and disease progression.