The pulmonary diseases most commonly recognized as being associated with the bronchial aspiration of material from the alimentary tract are suppuration and gangrene such as are observed in carcinoma of the esophagus or the aspiration of foreign bodies. A much more frequent pulmonary disease, aspiration bronchopneumonia, the pathogenesis of which seems not to be generally recognized, is also related to the aspiration of material from the alimentary tract, usually material from a dilated stomach. This form of aspiration bronchopneumonia is characterized by hemorrhage, hyperemia, edema and advanced postmortem and retrogressive changes in the lungs. Bronchopneumonia of the type usually believed to have its origin in the upper respiratory tract is considered to be caused by organisms aspirated from the pharynx or inhaled from the air, which lodge in the smaller bronchi on tissues already damaged by previous disease such as influenza, measles or other infections or colds. The incidence and