Objective To determine whether addition of oligosaccharides to a regular infant formula can lead to changes in the colonic function in vivo, particularly the fecal characteristics. Methods One hundred and two health full term infants were randomly assigned to one of two experimental formula groups: oligosaccharide formula (OF) group or regular formula (RF) group. Fifty breast-fed infants served as a control group during the same period. During the 3 weeks study, stool characteristics, including stooling frequency, stool consistency, pH and color, were recorded daily by parents. Results The mean fecal frequency of the infants in the OF group was significantly more than those of the RF group ( P ＜ 0. 05 ). The stools of the RF group were significantly harder than those in the OF group( P ＜ 0. 001 ). Although the mean stool pH score and stool color score of infants in the OF group were not significantly different from that of infants in the RF group, it was much closer to that of breast-fed infants. Conclusion The addition of oligosaccharides to a normal infant formula could lead to improvements in fecal characteristics.