The effects of cotton smoke injury on the phosphatidylcholine composition of pulmonary surfactant material were studied. While under halothane anesthesia, 18 ewes were intubated using a double-lumen tube. In six sheep the left lung was exposed to smoke; in another six sheep the right lung was exposed to smoke. A sham group of six sheep was insufflated with air instead of smoke. Twenty-four hours later the animals were killed, and alveolar lavage fluid was obtained from both lungs. Phospholipid material was separated, and its relative phosphatidylcholine composition was determined. In the smoke-treated lungs this composition was not different statistically when compared with the contralateral and the sham-exposed lungs. These findings suggested that smoke inhalation has no effect on the composition of the phosphatidylcholine fraction in the alveolar lining layer 24 hours after injury.