Anti-BB-antibody estimation was carried out in 100 cases of sarcoidosis, 40 cases of suspected sarcoidosis, 45 cases of pulmonary tuberculosis, 39 cases of pulmonary infections, 17 cases of bronchogenic carcinoma and 60 healthy persons as control. The result showed, that the patients suffering from sarcoidosis had the highest positive rate of anti-BB-antibody levels, whereas the positive rate of anti-BB-antibody levels in patients suffering from suspected sarcoidosis, pulmonary infections and tuberculosis was lower than that in patients suffering from sarcoidosis. Patients suffering from bronchogenic carcinoma and healthy controls had the lowest levels of anti-BB-antibody. It was suggested that sarcoidosis may have some relationship with infection.