We assayed the lipid content of bile from rats that had been fed either a standard diet (5% fat) or a high fat diet (25% fat, 1.2% cholesterol) in the presence or in the absence of various dietary fibers (namely, wheat bran, pectin and cellulose). The cholesterol concentration in bile from rats fed the high fat diet plus wheat bran or pectin was lower than that of the rats fed the high fat, high cholesterol diet without fiber. Bile phospholipids did not vary significantly from one group to another. In comparison to the standard diet, the high fat, high cholesterol diet led to a greater ratio of primary to secondary bile salts and a higher level of glycoconjugates. The observed differences may be explained by a variation in the metabolism of bile salts brought about by the difference in diet.