The kinetics of the alkaline hydrolysis of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in water/AOT/isooctane naicroemulsions has been studied by monitoring the absorbance change of the phenolphthalein in the system with time. The apparent first-order rate constant k(obs) has been obtained and found to be dependent on both the molar ratio of water to AOT omega and the temperature. The dependences of k(obs) on omega have been analyzed by a pseudophase model which gives the true rate constants k(i) of the AOT-hydrolysis reaction on the interface and the partition coefficients K(wi) for the distribution of OH(-) between aqueous and interface pseudophases at various temperatures; the latter is almost independent of the temperature and omega. The temperature dependences of the reaction rate,constants k(obs) and k(i) have been analyzed to obtain enthalpy, Delta H(not equal) entropy Delta S(not equal), and energy E(a) of activation, which indicate that the distribution of OH(-) between aqueous and interface pseudophases increases Delta S(not equal) but makes no contribution to E(a) and Delta H(not equal). The influence of the overall concentration of AOT in the system on the rate constant has been examined and found to be negligible. It contradicts with what was reported by Garcia-Rio et al.(1) but confirms that the first-order reaction of the AOT-hydrolysis takes place on the surfactant interface. The study of the influence of AOT-hydrolysis on the kinetics of the alkaline fading of crystal violet or phenolphthalein in the water/AOT/isooctane rnicroemulsions suggests that corrections for the AOT-hydrolysis in these reactions are required.