Objectives:  In this study we investigated the diagnosticvalue of polymerase chain reaction (PCR) which is fastand highly specific in terms of isolating  theMycobacterium tuberculosis (M. tuberculosis) from thebronchoalveolar lavage obtained by bronchoscopywhen tuberculosis is suspected in the patients withnegative sputum smears or when the sputum can notbe collected.Method: Our cases consist of patients who can notexpectorate or have three respective negative sputumsamples taken at the morning after starvation.Fiberoptic   broncoscopy was applied to all patients-under local anestesia-at the hospital. Lavages weretaken from bronchi, which were appropriate to thelesion. Lavage samples were sent to the laboratorywithout delay. Results were evaluated 2 days later.Totally 47 cases from 3rd Thoracic Diseases Clinic ofYedikule Thoracic Diseases and Thoracic SurgeryEducation and Research Hospital were included in thisstudy. Thirty-five of the cases had a higher possibilityfor tuberculosis, and the remaining 12 cases had noevidence for tuberculosis (control group). In thesecases  M. tuberculosis complex DNA specific IS6110field has been investigated by PCR and the results werecompared with the microbiological culture, lavage AFB.Results: Twenty-one of 35 patients in the study grouphad positive lavage PCR results. Fourteen patients hadnegative lavage PCR results. Four of 21 lavage PCR-positive patients were found to be ARB positive bylavage. Nine of  21 lavage PCR positive patients werefound to be ARB positive by culture. We had no falsepositive results. All control cases were negative interms of AFB smear, culture, and lavage PCR.Lavage PCR sensitivity and specificity calculationswere compared with ARB culture and lavage results.Considering the culture positivity as gold standard, thesensitivity and specificity of PCR were 60% and 100%respectively.Conclusion: PCR can be used as a supportivediagnostic test providing rapid and accurate results, iftuberculosis is suspected clinically and radiologicalyin patients with three consecutive AFB smear-negativesputum specimens or when the sputum can not becollected.Key words: Mycobacterium tuberculosis, polymerase chainreaction, bronchioalveoar lavage