The effects of the first pressure and/or number of passes through the homogenizer, and preagitation by an agitator, on the physical properties of emulsion bases were investigated. The first pressure of the homogenizer was varied in the range of 130 to 490kg/cm², and the second pressure was kept constant at 60kg/cm². Emulsifiers used were commercial grade Tween 80 and Span 20. Oil and water phases were liquid paraffin and distilled water, respectively. Emulsion stability was evaluated in terms of the following three physicochemical parameters : (1) particle diameter, (2) separation rate of water phase, (3) rheological properties of emulsion products. The following results were obtained. (1) With increases in agitation time and in intensity of agitation, the particle diameter of the emulsion became smaller. (2) The viscosity of emulsion prepared in the homogenizer increased remarkably with increase in the number of passes through the homogenizer. (3) The particle diameter of the emulsion was greatly decreased by the homogenizer only at the first pass. (4) Pre-agitation with an agitator is very useful for the preparation of emulsion products by means of a homogenizer.