Complex examination including the Mantoux test with 2 TU of PPD-L and tween-80 and fluorography was applied to 2537 underground miners aged 20 to 60 years. Negative, doubtful and positive tuberculin reactions were stated in 3.1 +/- 0.3, 3.7 +/- 0.4 and 93.2 +/- 0.5 per cent of the miners, respectively, including 1.4 +/- 0.2 per cent of the miners with hyperergic reactions. Relationship was found between the tuberculin sensitivity and occupational factors, as well as characteristics of the residual lesions of sustained pulmonary tuberculosis.