We attempted to detect an early rise in antibody titers to Borrelia burgdorferi in the serum of patients with erythema migrans of Lyme disease by utilizing B. burgdorferi isolates obtained from patients' own skin lesions instead of the B31 reference strain. B. burgdorferi was isolated from nine of 23 skin biopsy specimens submitted for culture. Elevated antibody titers were not detected in any of the 23 acute serum samples by immunofluorescence assay. The antigens derived from patient isolates were no more effective than the reference strain in detecting antibodies in patients with early Lyme disease.