Fine and uniform oil-in-water emulsions were prepared by surfactant (D) phase emulsification. Polyols were essential components for this purpose. To understand the functions of polyols, the solution behavior of nonionic surfactant/oil/water/polyol systems were investigated by the ternary phase diagrams of oleyl poly (oxyethylene) ether/liquid paraffin/polyol aqueous solutions. The addition of alkenediols: 1, 3-butanediol, 1, 4-butanediol, and 1, 2-propanediol, increased the solubility of oil in the isotropic surfactant phase and the mutual solubility between the aqueous solution and surfactant. The addition of other polyols : glycerol, polyglycerol 500, polyethylene glycol 400, 600, and D-sorbitol, had the opposite tendency. Alkanediols have been found to give finer oil-in-water emulsions than those of the other polyols, and other polyols to be useful for emulsification by hydrophilic surfactants.