Recent development in thepolymerase chain reaction (PCR) has brought an extraordinary opportunity for the rapid detection of M. tuberculosis in clinical specimens for the diagnosis of tuberculosis. Pneumoconiosis is a sort of pulmonary fibrosis consequent to inhalation of the respirable dust. The association between pulmonary tuberculosis and pneumoconiosis is well recognized. There is a 10-fold increase in the tuberculosis risk among the workers who have pneumoconiosis demonstrated by chest roentgenogram. The physicians managing the patients with pneumoconiosis have to maintain a high index of suspicion for the development of mycobacterial infection, since the diagnosis of tuberculosis is often difficult. Mycobacterium tuberculosis is a very slow growing organism and acid-fast bacillus (AFB) staining frequently shows false negative results, and therefore PCR would be a very rapid, easy and sensitive diagnostic method for the diagnosis of Mycobacterium tuberculosis in pneumoconiotic patients. To compare the PCR method with the conventional methods in diagnosing Mycobacterium tuberculosis in sputum, we used the sputa of 115 pneumoconiosis patients in Munkyeong Cheil Hospital. Of 32 pulmonary tuberculosis in the pneumoconiosis patients, 29 were PCR positive and were higher than 28, 20 positive by culture and AFB stain. Overall sensitivity, specificity, and which were 90.6, 91.5 % respectively for the PCR assay, 87.5, 100 % for the culture method ; 62.5, 98.7 % for the AFB stain. The PCR assay is a rapid, efficient, sensitive method which can detect M. tuberculosis directly in pneumoconiosis patients, and further study should be followed for the development of the easier method.