The genesis of auto-immune antibodies directed against the own tissue antigens of a host may be due to the host's immune response to mycobacteria. The prospective study included 110 patients treated for active pulmonary tuberculosis and the control group of 60 healthy subjects, volontary blood donors. Applying the method of indirect immnunofluorescence and cryostat sections of rat organs and human larynx cancer epithelial cell line (HEp-2 cells), the prescence of the following autoantibodies in the serum of the examined patients was examined: anti,nclear (ANA), anticardiac (ACA), antimitochondrial (AMA), antiparietal (APA), anti smooth muscular (ASMA), antithyroidal (ATA), rheumnatoid factor (RF). These autoantibodies were determined in the course oftreatment and five years later. Low levels of some examined autoantibodies were detected in the serum of a number of the examined patients. No significant difference in the presence of the analysed antibodies was registered between the sexes. In the course of the treatment a reversible hyper-gammaglobulinemia developed, which was at least partially due to the presence of autoantibodies in the patients blood serum. Besides possibly involved mechanisms of molecular mimicry and polyclonal lymphocyte activation, the presence of antinuclear antibodies in the patient's serum is at least partially due to isoniazide treatment. The finding of other autoantibodies is nonspecific and not related to the mycobacterial infection or antituberculosis drug administration.