A 66 year old woman with a history suggesting a tick bite on the right arm developed a slowly expanding erythematosus lesion. Similar lesions appeared on the trunk and extremities in the following months. A skin biopsy showing spiral shaped agents and the clinical findings were compatible with erythema chronicum migrans. A course of penicillin resulted in complete resolution of the lesions. After a 2 year follow up period she remains free of rheumatic, neurologic or cardiac lesions of Lyme's disease.