The author reports the observations over 190 patients referred to the Tuberculosis Institute for the present or suspected pulmonary tuberculosis of the lower lobe localization. In 47 (24.7%) of the patients the diagnosis of tuberculosis was rejected and lung cancer was diagnosed, central--in 5 of them, peripheral--in 42. Clinical manifestations in patients with tuberculosis and cancer were similar, weakness, cough, poor appetite being predominent; however, in cancer patients these were more frequently observed and more manifest with a tendency to aggravation and showing no response to tuberculostatic drugs. In 26.6% of patients with pulmonary tuberculosis and in 21.3% of lung cancer patients clinical manifestations of the disease were either entirely absent or insignificantly pronounced.