Bioavailability of dietary iron is affected by many factors in the diet. But the mechanism of iron translocation from intestinal lumen to the mucosa cell and its regulation are obscure. Previous research has shown a possible role of fatty acids in the brush-border membrane as an iron carrier. To investigate the influence of dietary fats on the composition of funy acids of the intestinal brush-border membrane and the relationship of fatty acids to iron uptake, three different dietary filts, safflower oil, olive oil and liquid lard, were fed to rats fi)r 4 weeks. The intestinal brush-border membrane was isolated and assayed Jbr fatty acid composition. Also iron uptake by these membrane vesicles was determined. The data show that rats fed safflower oil had a higher proportion of linoleic acid (18:2) in their intestinal brush-border membrane, but those fed olive oil possessed more oleic acid (18 : I) in the brush-border membrane. Iron uptake by the brush-border membrane vesicles was highest in the saJflower oil group. These results indicate a modification of fatty acid composition in the intestinal brush-border membrane by dietary fat and a possible correlation of changes in iron uptake.