Fourteen subjects with reversible obstructive lung disease inhaled one per cent lidocaine mist delivered by an ultrasonic nebulizer. The effect of ultrasonic nebulization per se was evaluated by a control study utilizing normal saline. After lidocaine inhalation there was a significant decrease in expiratory flow and an increase in airway resistance compared with either baseline or post-saline values. The changes were mild and do not preclude the continued use of nebulized lidocaine as an adjunct to bronchoscopy, but caution in its use is indicated.