The level of antibody of Borrelia Burgdorferi in the serum of 40 patient, 23 with sarcoidosis and 17 without sarcoidosis was determined by using ELISA method. Antibody of BB was positive in the serum of 18 patients with sarcoidosis (78.3%). It is possible that sarcoidosis might be a disease of autoimmune abnormality and antibody of BB in the serum an auto-antibody resulting from the stimuli of certain unknown antigens. Cross reactivity may be present between the serological tests for sarcoidosis and those for rheumatic disease, tuberculosis, tumour and Lyme disease. But another case might be that antigen of BB is a mixture. Different antibodies of different disease react with different component of antigen of BB. Therefore, antibody of BB can not be considered as a specific test in the diagnosis of sarcoidosis.