Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) characterized by inflammation, demyelination, gliosis, and neuronal loss. Pathologically, perivascular lymphocytic infiltrates, and macrophages produce degradation of myelin sheaths that surround neurons. Neurological symptoms vary and can include vision impairment, numbness and tingling, focal weakness, bladder and bowel incontinence, and cognitive dysfunction. Symptoms vary depending on lesion location. Clinical symptoms characterized by acute relapses typically first develop in young adults. A gradually progressive course then ensues with permanent disability in 10 to 15 years. MS groups into seven categories based on disease course: 1) Relapsing-remitting (RR): 70 to 80% of MS patients demonstrate an initial onset characterized by a relapsing-remitting (RR) course, demonstrating the following neurologic presentation: New or recurrent neurological symptoms consistent with MS. Symptoms last 24 to 48 hours. They develop over days to weeks. 2) Primary progressive (PP): 15 to 20% of patients present with a gradual deterioration from the onset, with an absence of relapses. 3) Secondary progressive (SP): this is characterized by a more gradual neurologic deterioration after an initial RR course. Superimposed relapses can be a feature of this clinical course, as well, although this is not a mandatory feature. 4) Progressive-relapsing (PR) MS: in 5% of patients, a gradual deterioration with superimposed relapses occurs. The following three categories are sometimes included in the spectrum of MS: 5) Clinically isolated syndrome (CIS): often classified as a single episode of inflammatory CNS demyelination. 6) Fulminant: characterized by severe MS with multiple relapses and rapid progression towards disability. 7) Benign: a clinical course characterized by an overall mild disability. Relapses are rare. When discussing MS, clinicians most often describe the RR course, considering its high prevalence amongst affected patients. Relapses often recover either partially or completely over weeks and months, frequently without treatment. Over time, residual symptoms from relapses without complete recovery accumulate and contribute to general disability. The diagnosis of RR MS is made with at least two CNS inflammatory events. Although different diagnostic criteria have been used for MS, the general principle of diagnosing the RR course has involved establishing episodes separated in "time and space." This means that episodes must be separated in time and affect different locations of the CNS. Making the diagnosis of MS expeditiously allows for the early and effective institution of disease-modifying therapy. Treatment aims at decreasing relapses and MRI activity. Long-term therapy aims at reducing the risk of permanent disability.