The bronchodilating efficacy of two doses of Atrovent are studied: the first dose is of 60 mg applied by inhaling once only; the second dose is of 240 mg applied also by inhaling but in divided 4 single doses of 60 mg taken at one hour intervals. 14 asthmatic patients were examined--7 patients with atopic bronchial asthma and 7 patients with non-atopic form of the disease. To all patients the 240 mg dose of Atrovent was given. To 10 of the patients the single 60 mg dose of Atrovent was given at the same conditions but in another day. The larger dose exerts a better and more prolonged bronchodilating action. An optimal dose of 180 mg of Atrovent given by inhalation in divided doses of 60 mg at one hour intervals is recommended. The last 60 mg Atrovent of the 240 mg dose used in the experiment do not improve the immediate bronchodilation which is probably due to a blockade of the receptors by the drug.