This proposal relates to the study of adsorption of n-dodecyl phosphocholine (C12PC) at the oil-water interface. The thickness of the adsorbed monolayers measured for dC12hPC will be compared to our previously published results for the dC16hPC. These data will be then compared with published data for these systems at the air¿water interface. We would deduce the role of alkyl chain length (increase by four methylene groups) on the conformation of this water-soluble, zwitterionic surfactant at the oil-water interface.