NMR line shape analysis has been used to monitor the rate of solute transfer across interfacial layers around emulsion droplets. For this purpose, emulsions of o-xylene in water stabilized by nonionic emulsifiers were prepared in which 1,4-dioxane was partitioned between the two phases. Because of the different magnetic susceptibilities of the xylene and water, two chemically shifted, exchange-broadened signals were observed from the dioxane. By simulating the spectra, the average residence time of a dioxane molecule in an oil droplet was obtained. The average time for a dioxane molecule to diffuse from within a droplet to the interface can be estimated from the droplet size distribution. Comparison of the diffusion and residence times then gives the probability that a dioxane molecule will transfer into the aqueous phase on arrival at the droplet interface. Addition of alkali-metal halides to the aqueous phase reduced the probability of transfer. For sodium salts, the magnitude of the reduction is in the order F - > Cl- > I-. LiCl, NaCl, and KCl produced similar effects.