The goal of this study was to compare thestool-softening effects of olestra and wheat bran and todetermine if changes in patterns of propagating colonicmotility were associated with the observed stool softening. Mini-pigs were fed chow (control) orchow supplemented with olestra (80 g/day) or wheat bran(80 g/day) for four days. Proximal colonic motility wasmonitored continuously, stool viscosity and fecal output measured daily, and cecal-to-analtransit time determined. Compared to controls, olestraand wheat bran significantly softened stool but had noeffect on fecal wet weight or colonic transit time. Neither olestra nor wheat bran changedthe number of propagating contractions per day,amplitude, motility index, propagation velocity, or therelative distribution of fast and slow propagatingcontractions. Our data suggest that the stool-softeningeffects of olestra and wheat bran are not due to directstimulation of propagating contractions in the colon ofthe mini-pig.