In a study on 121 consecutive patients with erythema migrans, 65 patients obtained oral penicillin, 36 tetracyclines, and 20 amoxicillin-clavulanic-acid. Follow-up was carried out for a median of 29, 17, and 7 months, respectively. In another limited trial on 29 patients with acrodermatitis chronica atrophicans (ACA), 14 patients received oral penicillin, 9 parenteral penicillin, and 6 ... [Show full abstract] tetracyclines. There was no statistically significant difference among treatment groups in both therapeutic trials, with the exception of different follow-ups due to the nonrandomized study design and different occurrence of the Jarisch-Herxheimer reaction in patients with erythema migrans. Later extracutaneous manifestations developed in 27% of the patients with erythema migrans and in 47% of the patients with ACA despite antibiotic therapy. We could not prove the superiority of any antibiotic tested in either early or late European Lyme borreliosis.