Neutron specular reflectance studies of the monolayer formed at an air-liquid interface by a novel synthetic nonionic surfactant 1,2-di-O-octadecyl-rac-glycerol 3-(omega-methoxydodecakis(ethylene glycol) have been used to determine the structure of the monolayer as a function of surface pressure, in particular to obtain the surfactant area per molecule and the thickness and degree of hydration of the monolayer. The molecular area data were then employed in generating a computer model for the three-dimensional structure of the small unilamellar vesicles formed by the surfactant. Comparisons between the three-dimensional structures of the nonionic vesicles and those formed by the corresponding glycerophospholipid are discussed in the context of their applications as vehicles for drug delivery.