Chronic relapsing experimental allergic encephalomyelitis (CR EAE) was induced in Lewis rats by inoculation with guinea-pig myelin and complete Freund's aduvant followed by treatment with low dose cyclosporin A. Histological, histochemical and electron microscopic studies of the lesions during the first and the second clinical episodes, as well as during the first and the second remissions, revealed inflammation, prominent demyelination, remyelination and gliosis in the central nervous system (CNS). This model of CR EAE in the Lewis rats may be a useful model for multiple sclerosis.