Peripheral blood lymphocytes from 60 black patients with Mycobacterium tuberculosis disease proved by culture and 100 healthy black persons were HLA phenotyped using a standard lymphocytotoxicity test. Statistical analysis showed that only Bw15 antigen had a significantly increased frequency among patients with tuberculosis when compared to healthy persons. Examination of disease manifestations among patients with tuberculosis demonstrated that patients with Bw15 had significantly more far-advanced pulmonary disease with cavitation than did patients without Bw15. Bw15 may influence suscpetibility to tuberculosis and the course of the disease.