Antibody responses from 60 patients with Erythema migrans were studied during the period of May to October 1988. All were tested using indirect immunofluorescent assay. Antibody response from 25 (41.6%) patients were found. IgM and IgG antibodies were present in the same percent. Serums were tested in different periods after Erythema migrans appeared. More often antibodies were present after a second month after infection (57.2%). Antibody responses were tested owing to the effect of the therapy. The absence of antibodies in serums of treated patients was less frequent (33.2%) than in serum of nontreated patients (45.1%). These results are similar to reported in current literature.