The following study was designed to test the hypothesis that feeding infants with specific dietary ingredients may impact gastrointestinal (GI) tolerance. The objective was to compare GI tolerance of healthy infants to human milk (HM) and other infant formulas (OF). Of the 1,453 evaluable subjects, 134 received HM, 267 received HM + Similac Advance® (SA), 83 received HM + OF, 778 received SA, and 191 received OF only (mainly NAN® Nestlé or SMA® Wyeth). Infants fed SA had less regurgitation than NAN® Nestlé or SMA® Wyeth (p<0.01). Also, infants fed SA had a lower incidence of general intolerance, spit-up, hard stools, flatulence, and colic than infants fed OF. In conclusion, Similac Advance® is well tolerated in healthy infants and results in stool characteristics more closely related to infants fed HM than infants fed OF.