A comparison of patients with erythema migrans due to Borrelia garinii versus Borrelia burgdorferi has not been reported.One hundred nineteen patients from New York State with erythema migrans caused by B. burgdorferi were compared with 116 patients from Slovenia with erythema migrans due to B. garinii infection.Patients with B. garinii infection were older, more often reported a tick bite, and developed larger lesions (median largest diameter: 18 and 14 cm, respectively; p = 0.01) that more often had central clearing (61.2% compared with 35.3%; p < 0.0001). Patients infected with B. burgdorferi, however, more often had systemic symptoms (68.9% vs. 37.1%; p < 0.0001), including fatigue (p < 0.0001), arthralgia (p = 0.0003), myalgia (p < 0.0001), headache (p = 0.0008), fever and/or chills (p < 0.0001), and stiff neck (p < 0.0001), and more often had abnormal physical findings (57.1% compared with 11.2%; p < 0.0001), such as fever (p = 0.0002) or regional lymphadenopathy (p < 0.0001). There was a trend for more patients with B. burgdorferi infection to have multiple erythema migrans skin lesions (13.4% compared with 5.2%; p = 0.051), and among patients with multiple erythema migrans the number of lesions was greater in B. burgdorferi-infected patients (median: 5.5 compared with 2.0; p = 0.006).The results of the present study indicate that in patients with erythema migrans the clinical features vary according to whether infection is caused by B. garinii or B. burgdorferi.