INTRODUCTION: Beneficial clinical effects of 4-aminopyridine (4-AP) in multiple sclerosis (MS) have been reported. The use of 4-AP in MS is based upon its ability to facilitate conduction in axons blocked by demyelination. This improvement is due to blocking of potassium (K+) channels in these fibres. Because K+ channels also play an important role in immune mechanisms successful treatment with K+ channel blockers in neuroimmunological diseases may have several causes. Therefore it seems important to study effects of K+ channel blockers in animal models of autoimmune disease. MATERIAL & METHODS: We studied the effects of 4-AP and quinidine on actively induced acute experimental allergic encephalomyelitis (EAE) in Lewis rats. RESULTS: There was no effect on the incidence of the disease. The severity of the disease was also unchanged although the disease duration was slightly diminished in the treated groups. Immunohistological comparison between the animals of different groups showed no differences. CONCLUSION: We conclude that 4-AP and quinidine are not capable of significantly changing the clinical course of EAE.