The efficacies of corticosteroids and azathioprine (part 1) and of cyclophosphamide, immune globulin, cyclosporine, interferons, copolymer 1, and cladribine (part 2) in patients with multiple sclerosis (MS) are reviewed. MS is an inflammatory, demyelinating disease of the CNS that commonly affects young adults. The involvement of various immune mechanisms in MS suggests a role for immunomodulating therapy. The goals of immunotherapy vary with the clinical stage of the disease and include (1) improving recovery from exacerbations, (2) decreasing the number or severity of relapses, (3) preventing the development of chronic progressive disease from a relapsing-remitting course, and (4) decreasing further progression in patients with chronic progressive disease. In clinical trials, corticotropin and corticosteroids have been found to accelerate recovery from exacerbations. Tapering is often effective after high-dose induction therapy. Long-term maintenance regimens do not alter disease progression and are not recommended. Azathioprine produces modest benefits with respect to relapse rates and disease progression after two or more years of treatment; adverse effects are mild to moderate. Azathioprine should not be used in patients with aggressive disease who may approach severe disability in 6-18 months. Cyclophosphamide, because of its modest impact on disease progression and its potentially severe adverse effects, including cancer, should be reserved for patients with aggressive relapsing-remitting or chronic progressive disease in whom other treatments have failed to work; maintenance therapy is necessary after induction. Intravenous immune globulin may benefit patients with severe relapses; however, its efficacy remains unproven. Cyclosporine also cannot be recommended because of its modest efficacy, marked adverse effects, and high cost. Interferon beta-1b is a more specific immunotherapy that has been found to decrease the number and severity of relapses. This treatment should be considered in patients with relapsing-remitting disease who are having two or more exacerbations per year. Copolymer 1 and cladribine have shown some promising early results. Although various immunotherapeutic drugs can provide relief in patients with MS, none is capable of reversing disease progression, and some can cause serious adverse effects. Better understanding of the immunologic basis of MS may lead to more specific immunotherapies with more lasting benefits.