Clinical picture of erythema migrans (EM) was evaluated in 83 patients from north-eastern Poland. Patients were in mean age of 42,8. Most of patients (71%) were women. Tick bite remembered 64% patients. Mean incubation period of EM was 33 days. The mean diameter of the skin lesions was 14.8 cm. They persisted for 2-270 (mean-54) days. Lesions were located mostly on the skin of lower extremities. The largest lesions were found on trunk and the smallest on lower extremities. EM of diameter exceeding 20 cm were observed in patients with longer history of the disease. Specific antibodies were found in 53% of cases and were present more frequently (78%) in patients with shorter incubation period (< 30 days).