Respiratory failure has become an increasingly frequent cause of death following shock or trauma. After the initial hemodynamic problems have been successfully treated, the patient's condition may appear to be satisfactory for variable periods of time, which may be as long as several days. Often, however, these patients then develop a progressive pulmonary insufficiency. These pulmonary problems are extremely difficult to treat unless they are recognized early in their development, and even then, success is not ensured. Although there has been extensive experimental work relating to the development of these lung changes, there is relatively little clinical data on this subject. In order to understand more clearly the effect of these pulmonary problems on prognosis, and to evaluate various methods for their early diagnosis, we have reviewed the records of 370 patients with shock or trauma seen in the Shock Unit and Intensive Care Unit of the Detroit General (Receiving)