A chronic remitting-relapsing form of experimental allergic encephalomyelitis (EAE) has been produced in monkeys sensitized to homologous myelin basic protein in Freund's complete adjuvants by the technique of suboptimal treatment after the onset of disease. Not only does the clinical course resemble that of human multiple sclerosis more closely than does the clinical course of acute EAE, but so also does the histological reaction, with more-nearly pure demyelination, rather than the hyperacute hemorrhagic-necrotic lesions that occur so commonly in untreated monkeys with ordinary acute EAE.