We have studied the preparation and stabilization mechanism of oil-in-water-type emulsions in the presence of amphiphilic 1:1 stoichiometric complexes of acylglutamic acids (CnGlu) with tertiary alkylamines (CnDMA). Relatively stable emulsions were obtained when Cl6Glu-C16DMA (or C18Glu-C18DMA), hexadecane, and water were homogenized at 80 degrees C and then stored at room temperature. The gel-liquid crystal phase transition temperatures (T-c) of C16Glu-C16DMA and Cl8Glu-C18DMA dispersed in water were determined to be ca. 39 and 53 degrees C, respectively. This indicates that the complexes form an adsorbed layer at the oil/water interface during the homogenization process above the T-c and then change into a gel during storage at room temperature. The gel phase formed at the oil/water interface prevents the oil droplets from coalescing. In contrast, shorter chain analogues (C10Glu-C10DMA and C12Glu-C12DMA) did not yield stable emulsions because their adsorption layers were not able to prevent coalescence of the oil droplets (i.e., the T-c of these analogues was below the room temperature). We have also demonstrated that the dispersion stability of these emulsion systems can be controlled by changing the aqueous pH.