The object of the study was to examine the efficacy of methods used in handling the aspiration syndrome. Fifty animals, grouped in two series, were studied. The first series (26 cats) served to establish the amount of 0.1 N HCl producing inflammatory changes and the time of their occurrence, and to ascertain whether the liquids and drugs used for instillation into the tracheo-bronchial tree produce morphologic changes in the lungs. The second series (24 cats) served to determine the therapeutic efficacy of instilling the aforementioned solutions and drugs after instillation of hydrochloric acid. The results obtained and a review of the experiments of others suggest that the treatment of aspiration chemical pneumonitis should be carried out by immediate instillation of small quantities of highly concentrated hydrocortisone into the tracheobronchial tree with supporting intramuscular or intravenous injections of that drug in the postoperative period, and simultaneous administration of antibiotics.