The polymerase chain reaction (PCR) technique was compared with the conventional smear and culture method for the detection and identification of Mycobacterium tuberculosis in 25 induced sputa samples. Sputum induction was performed with an ultrasonic nebulizer using 3% hypertonic saline in 27 previously untreated patients suspected of active pulmonary tuberculosis clue to chest X-ray findings, but who were unable to spontaneously expectorate sputum. All patients received anti-tuberculosis drugs for at least 6 months after sputum induction. Two patients could not expectorate sputum after hypertonic saline inhalation. Microscopy failed to detect positive acid-fast bacilli in 25 induced sputa samples. Induced sputa were both PCR- and culture-positive for 10 patients, PCR-positive and culture-negative for 4 patients, and PCR-negative and culture-positive for 2 patients. These results suggest that the PCR method is useful in diagnosing tuberculosis in induced sputum, and that the results of PCR and culture Procedures can complement each other.