The effects of dietary oils and fats used in Japan on the fecal contents of bile acids in rats were studied. F344/Du Crj female rats (8 weeks old) were fed on diet containing 20% corn oil, rape seed oil, sesame oil, soybean oil, lard, or tallow as high oil or fat diets or on 0.2% linoleic acid diet as a low fatty acid diet for 4 weeks, and then their feces were collected. Bile acids in the feces were partially purified and analyzed by high-performance liquid chromatography. Analyses showed that lard or tallow in the diet resulted in significant increases in the contents of bile acids in the feces, whereas sesame oil in the diet resulted in significant decreases in their contents.