The past decade has witnessed significant advances in the understanding of the pathophysiology of MS and in the development of novel disease-modifying agents (DMA). The use of DMA in the treatment of patients with MS has drastically increased not only in the United States but throughout the rest of the world. Currently, in the United States, most patients given a diagnosis of relapsing-remitting MS are commenced on a DMA. Controversy still exists regarding how early DMA should be commenced and whether all patients with relapsing-remitting MS should in fact be treated. To answer these questions, it is also important to know the natural history of the disease.