The results of bacteriological examination of materials collected by thin needle aspiration biopsy (TNAB) of the lung in patients with suspected cancer are presented. Koch's bacilli were detected in 67 cases per 1470 examinations performed for a period of 11 years. Positive bacterioscopic results were stated in 20 patients with negative cytological results. In 17 cases drug sensitivity of tubercle bacilli was determined which was important for the treatment tactics. The examination showed that the bacteriological detection of tubercle bacilli in the materials collected with TNAB was more simple and more available than cytological diagnosis of tuberculosis.