In 151 patients undergoing abdominal surgery, the bacteriologic status of the lower respiratory tract at the time of operation was determined by means of an endotracheal aspirate culture. A good correlation was found between the existence of chronic bronchitis as determined by respiratory history and by pulmonary function tests and the presence of bacteria, both pathogenic and nonpathogenic, in the lower respiratory tract. Among 11 patients with pathogens in the endotracheal aspirate, six of 54% developed postoperative pulmonary infections, whereas only 1.8% of those with no pathogens in the aspirate developed infections. In four cases, preoperative antibiotic therapy was associated with resistant pathogens in the endotracheal aspirate and postoperative pulmonary infection. On the basis of this study, an endotracheal aspirate culture is recommended in patients with chronic pulmonary disease. The isolation of a pathogen alerts the surgeon to the high risk of pulmonary infection with the same organism.