We compared the level of fecal bile acids and neutral sterols in 15 Japanese with large bowel carcinoma and 10 healthy controls. There was no significant difference in the amount of total fecal bile acids and neutral sterols between the patients and the controls. However, the amount of primary bile acids, especially chenodeoxycholic acid, tended to be higher in the patients. Conversely, lithocholic, beta-lithocholic and 3 alpha-hydroxy-12-ketocholanoic acid levels were higher in the controls. Trace amounts of 3 alpha-hydroxy-6-ketocholanoic acid were detected in some of the patients; none was found in the controls. Although a hasty conclusion should be avoided in the present study, it is of considerable interest that there was a difference in fecal bile acid composition between large bowel carcinoma patients and healthy controls.