High-dose intravenous immunoglobulins (IVIg) have become a successful new treatment regimen in neurological autoimmune diseases. Most autoimmune disorders are heterogeneous, implicating cellular and humoral immune mechanisms, and this pathogenesis also applies to MS. Many in vivo and in vitro experimental studies have shown that IVIg can therapeutically interfere with the immune system at several levels, but only some are likely to be relevant in MS. Clinical trials of IVIg have investigated the effect on different disease courses and stages of MS. Data show that IVIg have beneficial effects in relapsing-remitting disease, but probably no effect during the secondary progressive phase. IVIg are, therefore, currently considered in some countries as secondline treatments for patients with relapsing-remitting disease when first-line drugs are not tolerated. Despite promising data from animal experiments that IVIg may induce remyelination, human treatment trials have not demonstrated a clinically relevant improvement.