Introduction The last 15 years have witnessed great advances in the medical and surgical management of lung abscess. Reduction in morbidity and mortality from this disease has been brought about by the introduction of antibiotics, improved thoracic surgical techniques, and improvements in anesthesiology. The purpose of this paper is to review the experience in all patients with primary lung abscess at four large teaching hospitals in a metropolitan area.* Primary lung abscess is defined as a putrid cavity formation where no local predisposing factor can be demonstrated at the site of the abscess. Thus, abscesses which are secondary to bronchial obstruction by neoplasm, those resulting from necrosis in an area of tumor or pulmonary infarction, infected lung cysts, and those due to specific infections such as tuberculosis and fungus diseases, are excluded. The exclusion of secondary lung abscesses is necessary if valid conclusions are to be drawn concerning the course