The reaction rate studies on the hydrolytic cleavage of acetyl salicylate ion (AS(-)) within the [(OH)-O--] range 0.010-0.025 M reveal AS(-) and (OH)-O-- as the reactants. The effects of micelles of sodium dodecyl sulfate (SDS) on observed pseudo-first-order rate constants (k(obs)) for the hydrolytic cleavage of AS(-) have been studied at different [OH-]. At a constant [OH-], the rate constants (k(obs)) follow an empirical relationship : k(obs) = C + F[SDS](T) where [SDS](T) represents total SDS concentration. The magnitudes of C and F increase with an increase in [OH-]. These data are explained in terms of the pseudophase model of the micelle.