The kinetics of solvolysis of diphenylmethyl chloride, 4-nitrophenyl chloroformate, benzoyl chloride, p-anisoyl chloride, and bis(4-nitrophenyl)carbonate in water/AOT/isooctane microemulsions with various water/surfactant mole ratios W (AOT = sodium bis(2-ethylhexyl)sulfosuccinate) were interpreted by using a pseudophase model in which the substrates are assumed to be distributed between the isooctane and interface phases. The W-dependence of the intrinsic rate constants k for solvolysis at the interface depends on the solvolysis mechanism : for S(N)1 reactions, k decreased with W, which is attributed to decreasing polarity of the interface; contrariwise, S(N)2 reactions are accelerated by decreasing W, which is attributed to increasing nucleophilicity of interfacial water.