- Bronchoalveolar lavage (BAL) during fiberoptic bronchoscopy is being used increasingly for the investigation of asthma. Airway responsiveness to methacholine is a sensitive indicator of the presence and severity of asthma. Therefore, we studied the effect of BAL on methacholine airway responsiveness in stable asthmatics. Geometric mean methacholine PC20 was 1.34 mg/ml before and 1.80 mg/ml after BAL (p = 0.26) in asthmatics. Immediate symptoms of airway narrowing after BAL occurred only in the 3 asthmatics with moderate to severe hyperresponsiveness. These symptoms were rapidly relieved by inhaled bronchodilator. There was no relationship between the occurrence of symptoms and the amount of topical lidocaine used for local anaesthesia or the volume of lavage fluid returned. The absence of an effect of BAL on airway responsiveness supports the safety of this procedure in the controlled asthmatic patient with near normal FEV1, irrespective of the level of baseline airway responsiveness.