383 patients with a bronchial hyperreactivity were repeatedly investigated during an observation period of 3 up to 6 years. The inhalative provocation test with nebulized histamine solution was used. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were measured by spirometry. The reduction of FEV1 in per cent of the initial value marked the degree of the bronchial hyperreactivity. The normalization was depending on the degree of the initial bronchial hyperreactivity. In 148 patients (36.6%) the provocation test results were normalized, e.g. FEV1 decreased less than 15% of the initial value. Patients with a low degree of the bronchial hyperreactivity, that means a decrease of FEV1 between 15 and 30% of the initial value, demonstrated the normalization of the provocation test significantly more frequent than patients with a higher degree of bronchial hyperreactivity. There was a considerable difference in course of the bronchial hyperreactivity of smokers and non-smokers. The latter tended to a more frequent normalization. A further influence of the course was stated with the age of patients. The younger ones had a higher tendency to normalization. Patients suffering from asthma bronchiale were mostly in the group with a higher degree of bronchial hyperreactivity and showed a rather stable course of it.