In all the sera of four patients with meningoradiculitis of Bannwarth admitted to the neurological department of the University Clinic Grosshadern in Munich in 1983, we found antibodies against Ixodes dammini spirochetes. In three patients antibodies were also present in the CSF. In one patient, we isolated spirochetes from the CSF and demonstrated specific IgG antibodies in serum and CSF. This spirochete was morphologically indistinguishable from the I. dammini spirochete and a spirochete isolated from the thick I. ricinus in the Munich area. Despite distinct differences in the clinical manifestation of Lyme disease when accompanied by neurological complications and meningoradiculitis of Bannwarth, we suggest that both diseases are caused by spirochetes.