Although the etiology and pathogenesis of Multiple Sclerosis (MS) remain elusive, accumulating evidence indicates that MS is a chronic inflammatory disease with an autoimmune component, mediated by autoreactive T lymphocytes specific for myelin antigens. The triggering T cell autoantigen has not been identified yet, but recent immunological studies in MS and parallel experiments in experimental allergic encephalomyelitis (EAE), the animal model of MS, have indicated that myelin basic protein (MBP) can be considered as one of the major candidate autoantigens in the pathogenesis of the disease. Based on these observations, several therapeutic strategies have been developed aimed at the specific elimination or inactivation of MBP reactive T cells in MS. One of these approaches involves the immunization of MS patients with autologous attenuated autoreactive T cells to induce an immune response specifically targeted at these autoreactive T cells. This method, termed T cell vaccination, has been shown to prevent and treat EAE. We have recently conducted a pilot trial of T cell vaccination in a limited group of MS patients to evaluate the immunological responses to the injected cells. The data obtained indicate that this type of vaccination induces an effective anti-clonotypic T cell response leading to a specific depletion of circulating MBP reactive T cells. Preliminary data on the clinical effects are promising, encouraging further clinical trials.