Bronchial hyperreactivity (tested with 0.01% acetylcholine ultrasonic aerosol) and ventilatory inhomogeneity (tested with V2/V1-parameter of the flow-volume diagram) using the pneumotest apparatus were studied. Patients with high bronchial reactivity are frequently showing not only ventilatory disorders of distribution but sometimes also an additional increase due to the bronchial provocation. Bronchial reactivity testing combined with the flow-volume diagram allows to estimate the predominant site of the bronchospastic response either centrally or also in the more peripheral parts of the bronchial system. By testing bronchial reactivity persons without any symptoms and with no evident spirometric alterations can be separated in dependence on the relative increase of total airway flow resistance as well on smoking habits. That does not succeed with the appliance of the inhomogeneity parameters V2/V1. The results obtained in this study are of value for preventive measures, for early detection of risk factors in premorbid stages, for assessment of prognosis in chronic nonspecific lung disease, for an adequate therapy and also for the rehabilitation of patients in jobs with inhalation of noxious dusts.