Abstract: The concept of effective concentration of surfactant in membrane phase, which considers the high adsorption density of the surfactant at the droplet interface in LSM system was proposed. The effective concentration of surfactant, Csef, could be estimated by equations(7)-(9). Swelling caused by emuls-ifioation during the initial dispersion process was investigated. Data of swelling ratio were measured by a density method. A general model for estimating the "emulsification swelling" rate, Fse, was proposed on the basis of a mechanism of swelling due to the entrainment of water resulted from interfacial turbulence and emulsification in the initial dispersion process. Equation(26)gave excellent fit to experimental data of Fujinawa, et al. (1984, 1985) and the authors.