Relapsing experimental allergic encephalomyelitis (EAE), an autoimmune disorder resembling multiple sclerosis, has been produced by inoculating SJL/J mice with spinal cord or myelin basic protein in appropriate adjuvants. To determine whether initially sensitized lymphocytes or the persistence of antigen depots in the animal were responsible for the relapsing episodes of inflammatory demyelination, adoptive transfer studies were undertaken utilizing lymphocytes from relapsing EAE-immunized donors transferred directly or after in vitro culture. In direct-transfer studies donor lymphocytes produced clinical and pathological signs of relapsing EAE in 3 of 7 recipients of lymph node lymphocytes and 1 of 5 recipients of splenic lymphocytes. In vitro culture of lymphocytes in myelin basic protein or T cell growth factor prior to transfer increased both the incidence of disease and the number of animals having relapses, and allowed transfer with fewer lymphocytes. Because all animals had delayed onset of disease, this study demonstrates that the ability to develop relapsing inflammatory demyelination is transferable with lymphocytes and does not require the presence of antigen.