The partition behavior of ethyl gallate (EG), 3,4-dihydroxybenzoic acid ethyl ester (DHBEE), and p-hydroxybenzoic acid ethyl eater (PHBEE) in different systems was investigated using ultrafiltration and dialysis techniques. The proportion of solute solubilized by micelles or oil in surfactant solution and biphasic water-oil systems, respectively, was determined directly. To study the partition in oil-in-water (O/W) emulsions, a mathematical model is presented which differentiates between the solubilization capacity of oil, surfactant, and aqueous phase. In contrast to previous studies, this model focuses on the equilibrium between oil and surfactant in the lipid phase of emulsions. The mutual influence of oil and surfactant determining the solubilization equilibrium is described by nonlinear functions derived from the experimental data. The solubilization capacities of oil and surfactant in O/W emulsions differed markedly from the surfactant solutions and biphasic water-oil systems. According to their polarity EG, DHBEE, and PHBEE showed significant differences in their partitioning behavior in O/W emulsions composed of oil, buffer, and different surfactants (sodium dodecyl sulfate, SDS; cetyltrimethylammonium bromide, CTAB; polyoxyethylene 20 cetyl ether, Brij 58; Emultop, a partially hydrolyzed soybean lecithin, PHLC). For instance, the proportion solubilized by oil in SDS containing emulsions increased in the order EG, DHBEE, and PHBEE, but the proportion solubilized by the surfactant showed parabolic behavior. All experimental data were in good agreement with the data computed on the basis of the mathematical model described in this study.