Impairment of pulmonary function in chronic lung disease is due to many factors, related basically to the amount of fibrosis, the degree of emphysema and the status of the bronchial tree. Much of the disability produced by these factors is a result of altered pulmonary physiology rather than the effects of organic disease itself.1 2, The fibrosis and emphysema produce interference with pulmonary ventilation, faulty distribution of air in the lungs and ultimate oxygen unsaturation of the blood. Bronchial irritation, whether due to foreign body, infection, or abnormal secretions will produce increased breathing resistance through bronchospasm, narrowing of the airways and retention of secretions. The thickened, edematous and spastic bronchiolar mucosa plays a big part in producing unequal alveolar aeration and perfusion and constitutes a reversible factor in the production of disability. Measures for the relief of bronchospasm and evacuation of retained secretions have, therefore, been effective in improving pulmonary function. Barach, Segal, and others4’ #{176} o have amply shown the usefulness of aerosol therapy in this respect. Ajministration of aerosols generally depends upon the inspiratory effort of the patient to carry the vapor into the lungs. Frequently, however, adequate dissemination of the aerosol is prevented by physical limitations imposed by the fibrosis, emphysema and impaired diaphragmatic motion. To counteract the pathological alterations produced by these factors, Motley and his associates7’ ‘ ‘ 10 have developed the use of intermittent positive pressure breathing combined with simultaneous nebulization of bronchodilator agents, antibiotics and other suitable drugs. Since intermittent positive pressure breathing increases both the minute volume of ventilation and the respiratory excursions, it was apparent that the aerosolized vapor would be more uniformly and more effectively distributed throughout the lung with better relief of bronchospasm and promotion of bronchial drainage. The present report deals with our experience over the past four years with this form of therapy in chronic pulmonary disease. Method of Study The patients in this study consist of a group of 450 hard and soft coal