Experimental studies and open clinical trials have suggested intravenous immunoglobulin (i.v.Ig) as a potentially effective treatment of multiple sclerosis (MS). The Austrian Immunoglobulin in Multiple Sclerosis (AIMS) study tested this assumption by examining 148 patients with relapsing-remitting MS in a randomized, double-blind, placebo controlled fashion (75 i.v.Ig, 73 placebo). Monthly administration of i.v.Ig in a dosage of 0.15-0.20 g/kg over a period of 2 years slowed the progression of or even reversed disability as evident in a total of 24% of patients and almost halved the number of relapses in comparison to placebo treatment. Therapeutic efficacy was noted within the first 6 months of treatment and was not correlated to the severity of disability (mild neurological signs without disability to ambulatory with assistance) at study entry. Overall the magnitude of treatment effects of i.v.Ig was comparable to that reported for beta-interferon and copolymer 1. Further ongoing studies will have to clarify the future role of i.v.Ig in the treatment of MS, in particular in the progressive forms of the disease.