To examine the effect of dietary fat on lung lipids, male weanling mice (CD-1 strain) were fed purified diets containing 5% stripped lard or corn oil and kept in chambers supplied with air filtered free of airborne bacteria. Vitamin E was fed at 0, 10.5 or 105 mg dl-alpha-tocopheryl acetate/kg diet. Dietary fat and vitamin E (0 or 10.5 mg/kg) had no significant effects on the lung levels of triacylglycerol (TG) or phospholipid (PL) molecular species through 4 weeks of intake. Alterations in lung fatty acid composition were followed through 6 weeks of intake at 0, 10.5 and 105 mg vitamin E/kg diet. Vitamin E, at all levels of supplementation, had no significant effect on mouse lung fatty acid composition. Saturated fatty acids of the lung also showed little alteration by diet, but feeding the lard diet significantly elevated oleic and palmitoleic acids. In mice fed the corn oil diet the levels of linoleic acid (18:2) were twice those of lard-fed mice, and arachidonic acid (20:4) was elevated by 15.8%. The diet elevated the mean peroxidizability index (PI) on lung tissue in corn oil-fed mice.