This study investigates the stereospecific distribution of fatty acids across the triacylglycerol molecules in breast milk obtained at three different periods of lactation. Fatty acids were distributed within the three sn -positions of the glycerol backbone in a highly specific pattern; the shorter fatty acids tend toward the sn -2 and sn -3 positions of the glycerol molecule, whereas the longer chain fatty acids are more in the sn -1 and sn -3 position. Significant differences in fatty acid composition occurred between lactation times, but factors affecting the fatty acids content do not alter their regiospecific fatty acyl profile, although the quantities in each position can be changed. This suggests that the fatty acids regiodistribution profile in human milk related to the optimal infant growth should be used as a standard for the preparation of infant formulas.