Oxidation experiments of beta-carotene in the presence of alpha-tocopherol were conducted in a biphasic oil-water system having a definite interfacial area. The induction period in which the alpha-carotene concentration slowly decreased was about 1.6 times longer than that in the single oil phase system when the initial a-tocopherol concentrations were the same. The existence of the water phase suppressed the alpha-tocopherol consumption, resulting in a delay in the progress of the beta-carotene oxidation. A kinetic model was constructed by modifying the oxidation and antioxidation mechanisms of beta-carotene in tire single oil phase and incorporating the reaction of the alpha-locopherol peroxyl radical with the oxonium ion at the oil-water interface. The model quantitatively described the oxidation behavior of beta-carotene in the biphasic system over wide ranges of temperature, initial alpha-locopherol concentration and interfacial area.