Serum antibody to Borrelia burgdorferi was measured in 33 patients with sarcoidosis which was confirmed clinically and pathologically. The results showed that 81.8% of the patients were positive for anti-B. burgdorferi antibody. In addition, a strain of B. burgdorferi was isolated from a patient's blood. Fifteen patients received ceftriaxone 2g per day or penicillin 12 million U per day. The antibody titers of the patients decreased to nearly normal levels rapidly. Serum angiotensin converting enzyme (SACE) turned to normal range after the treatment. According to the findings mentioned above, we consider that B. burgdorferi infection may be the cause of sarcoidosis and sarcoidosis might be a specific type of Lyme disease.