We describe 3 cases of upper airway obstruction in which no organic cause could be identified. All 3 patients presented with severe dyspnea and stridor. Direct laryngoscopy and bronchoscopy failed to demonstrate any lesion. Flow-volume loops showed a pattern of severe variable extrathoracic airway obstruction with a decreased peak inspiratory flow and an increased ratio of the forced expiratory flow at 50% vital capacity to the forced inspiratory flow at the same lung volume. Plethysmographically measured airway resistance was normal in the 2 patients for whom it was obtained. We believe a functional etiology should be added to the possible causes of acute upper airway obstruction. This entity can readily be identified by the marked discrepancy between inspiratory flow limitation and airway resistance.