Multiple sclerosis (MS) is a chronic disease with an unpredictable clinical course and several distinct clinical patterns. Recent developments in immunology, molecular biology and genetics have improved our understanding of the pathophysiology of MS. Further, advances in trial methodology, including the availability of magnetic resonance imaging (MRI) as a surrogate outcome measure, have led to the identification of several new therapeutic options for relapsing-remitting (RR) MS. These therapies include corticosteroids, recombinant interferon-beta-1b (rIFN beta-1b), recombinant interferon-beta-1a (rIFN beta-1a) and copolymer-1 (Cop-1). Corticosteroids have been shown to accelerate the recovery from acute exacerbations, but there are still conflicting data on their effect on outcome and long term course. rIFN beta-1b, rIFN beta-1a and Cop-1 all effectively alter the natural history of RR-MS. These 3 agents all decrease the relapse rate by approximately one-third, but differ in their adverse effect profiles and administration regimens. Further trials are required to define the optimal treatment of RR-MS.