Eleven patients with neuro-borreliosis had been treated with 200 mg fluconazole daily for 25 days after an unsuccessful therapy with antibiotics. At the end of treatment eight patients had no borreliosis symptoms and remained free of relapse in a follow-up examination one year later. In the remaining four patients, symptoms were considerably improved. At the end of therapy immune reactivity (IgM+) disappeared in three patients. Since borrelia spp. are almost exclusively localised intracellular, they may depend on certain metabolites of their eucaryotic host cell. Inhibition of P450 and other cytochromes by fluconazole may incapacitate Borrelia upon longterm exposure.