A simplified kinetic model is presented in order to interpret the kinetics of the self-reproduction of vesicles. These experimental systems have been recently described (Walde P. et al., J. Am. Chem. Soc. 1994, 116, 11649) and consist of a biphasic system in which an insoluble surfactant precursor, e.g., an anhydride of a long-chain fatty acid, is overlaid on a basic aqueous solution and is eventually hydrolyzed into surfactant molecules that then assemble spontaneously into vesicles. Under these conditions, a catalytic effect can be observed due to the presence of the aggregates in the aqueous solution. To elucidate this effect within a theoretical framework, the hydrolysis has been described as an irreversible surface reaction that can take place both at the macroscopic interface and on the surface of vesicles. This reaction has been also assumed to be the limiting step so that all the others processes (e.g., formation of vesicles, absorption of molecules anhydride by vesicles, acid-base reactions, etc.) have been considered as equilibrium processes. On the basis of these assumptions, the catalytic effect has been interpreted as mainly due to the large growth of the reaction surface and it has been possible to kinetically describe two different self-reproducing systems of vesicles. The good agreement obtained between the experimental data and the theoretical forecasts supports the validity of this approach.