Prior studies have demonstrated that glucocorticoids can influence the structure and function of several different organs, including the small intestine. However, to date, the effects of glucocorticoids on the glycosphingolipids of the rat small intestinal mucosa have not been examined. In the present experiments, male albino rats of the Sherman strain were subcutaneously administered dexamethasone (100 micrograms/100 g body wt. per day) or diluent for 4 days, and the ceramide, acidic and neutral glycosphingolipid compositions of the proximal small intestine of these animals were examined and compared. The results of these studies demonstrate that dexamethasone administration: (1) increased the content and relative percentage of hematoside (GM3) in this tissue; (2) increased the percentage of N-glycoylneuraminic acid of hematoside; (3) decreased the percentage of the long-chain base phytosphingosine of hematoside, glucosyl- and globotriaosylceramide; and (4) did not appear to influence significantly the concentration of the neutral glycosphingolipids or ceramide in this tissue. These data, therefore, indicate that dexamethasone administration induces alterations in the glycosphingolipids, particularly hematoside, of rat small-intestinal mucosa.