Ten healthy male subjects on a low fiber diet were given two doses of raw wheat bran (12 and 20 g/day) and two doses of cooked bran (13.2 and 22 g/day). Both doses of raw bran increased fecal dry weight but only the higher dose decreased transit time and increased stool volume. Individual stool size was increased only by raw bran 12g/day. Neither bran influenced fecal wet weight or stool frequency. This study suggests that the cereal manufacturing process alters wheat bran so that cooked bran has less effect on the intestine than does a comparable amount of raw bran.