The intravenous administration of high doses of immunoglobulins pooled from the plasma of healthy donors (IVIg therapy) has beneficial effects in patients with a variety of autoimmune disorders. These clinical observations indicate that IVIg have potent antiinflammatory characteristics, and identification of the precise mode of action may open up perspectives for future therapeutic strategies. In certain tissue-specific autoimmune disorders like multiple sclerosis (MS), self-reactive T cells recognizing autoantigens play a significant role for disease pathogenesis, as these cells are able to initiate, maintain, and propagate the harmful immune attack in experimental animal models of disease. These findings render self-reactive T cells an important therapeutic target for autoimmune diseases. Here, we review the effects of IVIg on the homeostasis of T cells and discuss the possible therapeutic implications for multiple sclerosis. As supported by several experimental studies, IVIg regulate crucial steps of T cell-mediated immune responses. These effects involve the modulation of activation, proliferation, differentiation, apoptosis, and effector mechanisms of T cells. The pattern of IVIg-T cell interactions is complex, as IVIg may directly bind to regulatory structures on T cells, or modulate T cell functions indirectly via soluble or cellular components of the immune system.