Retro-inverso modification of peptides preserves parent peptide overall topology and provides at the same time stability to proteolysis, leading to derivatives with prolonged half-life in vitro and in vivo. In this study the encephalitogenic epitope P87 - 99 of myelin basic protein has been prepared in the retro-inverso form to examine its biological activity in a murine model of multiple sclerosis. Experiments of in vivo T cell tolerance induction in SJL mice revealed that the retro-inverso peptide was able to induce a selective T cell hyporesponsiveness, as measured by a reduction in the proliferative response of lymphnode T cells after antigen challenge. Oral administration of retro-inverso peptide decreased the disease severity significantly and delayed considerably the disease onset in treated mice. Enhancement of resistance to proteolysis by retro-inverso modification of encephalitogenic epitopes may increase the therapeutic value of oral tolerance induction in the treatment of multiple sclerosis and other Th1-associated inflammatory disorders.