Diosgenin and beta-sitosterol (1% in diet) were administered to CRJ:CD-1 male mice for 15 days, in order to examine the changes in bile acid metabolism. There were some differences between diosgenin and beta-sitosterol in their effects on diet intake, liver weight, and plasma cholesterol level. However, both phytosterols caused no statistically significant changes in body weight gain, decreased cholesterol absorption to about one-third that observed in control mice, decreased liver cholesterol level, increased fecal excretion of cholesterol, and decreased fecal excretion of bile acids. Most of the increase in fecal excretion of cholesterol occurred 2 days after the start of feeding of phytosterols and gradually declined thereafter, but the levels on day 15 were nevertheless higher than those in the control mice. The fecal excretion of bile acids decreased progressively after the treatment with phytosterols. The decrease of bile acid derived from chenodeoxycholic acid was more predominant than the decrease of those derived from cholic acid, resulting in an increase of the cholic acid/chenodeoxycholic acid ratio. The biliary cholesterol, phospholipid, and bile acid mole % ratios and the lithogenic index were not changed, but the percentages of cholic acid and its related bile acids (the cholic acid group) to the total bile acids increased and those of the chenodeoxycholic acid group decreased after the treatments. The pool size of bile acids decreased in the mice given diosgenin but not in those given beta-sitosterol. Distribution of bile acids between the gallbladder and intestine was not altered by either phytosterol.(ABSTRACT TRUNCATED AT 250 WORDS)