The examination involved 130 persons aged 2 to 67, including 82 women and 48 men. 60 persons were sent to be serologically examined after their antibiotic therapy had begun. ECM was clinically diagnosed in all the persons. 78 patients (60% of the whole group) recolected anamnesis being bitten by a tick. All the persons were subjected to an immunoenzymatic examination by the ELISA method using fluorofast produced by 3M American company. In a group of 70 who had shown Borrelia burgdorferi antibodies before treatment there were 23 patients with negative and 47 with positive or very positive readings. The antibiotic therapy was followed by remission of clinical symptoms and gradual seronegativisation. The routine medical procedure in ECM cases should include serological test and an antibiotic treatment should be applied. Neurological check-up seems to be advised.