A thirty-three-year-old patient developed polyradiculoneuritis with several post-therapeutic relapses despite excellent response to treatment by intravenous polyvalent gammaglobulin. After the second relapse, positive titres for Borrelia burgdorferi were found in serum and C.S.F. We gave her intravenous antibiotic and clinical signs and electrophysiological data improved. Our report and the literature can distinguish two clinical and electrophysiological presentations of neurological peripheral involvement in Lyme disease: meningoradiculoneuritis with axonal involvement and polyradiculoneuritis with demyelinization.