Acacia coacervated by gelatin, without any cross linking agent, was found to be an excellent stabilizer for medicinal emulsions. The thickness and some properties of interfacial films of gelatin-acacia mixture formed at oil-water interface have been studied. Viscosity measurements and serial washing of the disperse phase have been used. Gelatin-acacia coacewates stabilize oil-in-water emulsions by forming strong interfacial films, although their mean film thickness is about the same thickness as those of gelatin or acacia used separately. Because of the irreversible adsorption of these macromolecules at the interface which forms a strong and relatively insoluble coacervate film, stabilization of medicinal disperse systems by coacervation seems to be of practical use.