Abstract: The breakage of liquid surfactant membrane (as determined by leakage ot K ons from the internal phase to the external phase) was investigated. A physical model that leakage will occur only when the external and internal interfacial membranes are simultaneously broken, was proposed to describe emulsion breakup. On the basis of this physical model, a mathematical model for estimating the breakage rate, Kb, was developed. The predicted values by means of the above equation agreed well with the experimental data of Fuji-nawa (1984), Ma Xinsheng (1987) and the authors.