The relationship between the emulsion stability of phosphatidylcholines (PCs) and their headgroup motion of varied acyl chain lengths was investigated by 31 P and 13 C NMR. The acyl chains of PCs at glycerol sn-2 were shortened by the acylation of lysophosphatidylcholine (LPC) with C 2 -C 10 acids, and PCs with short glycerol sn-1 and sn-2 chains were also synthesized by the acylation of glycerophosphorylcholine (GPC) with C 6 -C 10 acids. Their physical properties and emulsion stability were compared with those of an equimolar mixture of egg PC and LPC, and similarities of the headgroup motion and emulsion stability were found between some short-sn-2-chained PCs and the mixture of PC and LPC. The results suggested that the headgroup motion correlated with the interfacial absorptivities of PCs and with their emulsion stability