We have studied 113 patients with neurologic Lyme borreliosis and meningitis who were treated with intravenous high-dose antibiotics (penicillin G, 12 g, mostly for 14 days in 47 patients; penicillin G, 9 g, mostly for 10 days in 58 patients; doxycycline, 200 mg, in 5 patients; and cefuroxime, 4.5-9 g, in 3 patients). Seventy percent of the patients had peripheral nerve symptoms and 13% had central nervous symptoms. Almost half of the patients were treated more than 4 weeks after the onset of symptoms and 15% of the patients had persisting or progressive symptoms between 4 and 11 months. There seemed to be clinical benefit as well as a decrease of spinal fluid pleocytosis and spinal proteins. No significant symptoms of Herxheimer reaction were demonstrated.