Follow-up of 57 patients who suffered from antibiotically untreated acute, monophasic neuroborreliosis 5 to 27 years ago shows no significant difference in comparison with the follow-up of 66 patients who suffered from antibiotically treated acute, monophasic neuroborreliosis during the last 5 years. In both groups, the involution of clinical symptoms and the normalization of pathological CSF findings were nearly identical. We found no significant difference of sequelae between the groups. Following acute neuroborreliosis, neither the antibiotically untreated nor the antibiotically treated patients developed chronic neuroborreliosis. Only in rare cases of primary chronic neuroborreliosis with CNS involvement did we observe convincing effects of antibiotics, which were given mostly in combination with glucocorticosteroids.