From observational studies and positive experience in other autoimmune disorders it has been speculated that intravenous immunoglobulin (IVIG) may be effective for the interval treatment of MS. The Austrian Immunoglobulin in Multiple Sclerosis (AIMS) study was the first to test this assumption in a randomized, double-blind, placebo controlled trial of 148 patients with relapsing remitting MS. IVIG given monthly at a dosage of 0. 15-0.2 g/kg bodyweight over 2 years was associated with a significantly more favourable course of disability as measured by the EDSS (- 0.23 vs 0.12; P=0.008) and caused a significant reduction of the frequency of relapses (0.52 vs 1.26; P=0.011). Beneficial effects on these outcome measures were already seen within 6 months of treatment and did not appear to depend on the severity of baseline disability. IVIG treatment also had a positive effect on daily and social living according to patient' self rating on the Incapacity Status and Environmental Status Scales and was associated with a lower, though not significantly different number of hospital admissions and days spent in hospital. These data support IVIG as an alternative treatment option for relapsing-remitting MS and encourage further studies to clarify the optimal usage of this substance for this indication.