Some patients with endobronchial tuberculosis (EBTB) have wheeze on physical examination and normal chest PA, which mimic bronchial asthma. Non-specific bronchial challenge tests have been used to confirm the presence of bronchial hyperreactivity, which is a hallmark of bronchial asthma. To evaluate the effect of endobronchial tuberculous inflammation on bronchial responsiveness to histamine, the provocation concentrations of histamine required to reduce FEV1 by 20% of the pre-challenge baseline (PC20) were compared between patients with EBTB, patients with symptomatic bronchial asthma and normal, healthy controls. PC20 in EBTB patients (17.2 +/- 2.3 mg ml-1) and normal controls (19.5 +/- 1.4 mg ml-1) were significantly higher than in bronchial asthma patients (0.99 +/- 0.15 mg ml-1). PC20 in EBTB patients was not affected by disease location in the bronchial tree was not correlated with FVC or FEV1. In conclusion, one should consider the possibility of EBTB for differential diagnosis from bronchial asthma, if airway responsiveness appears normal in wheezy patients.