The effects of mixed sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTABr) surfactants on pseudo first-order rate constants (k(obs)) for methanolysis of ionized phenyl salicylate (PS-) and alkaline hydrolysis of phenyl benzoate (PB) reveal the presence of micelle type aggregates or micelles, anionic in nature when X greater than or equal to 4 and cationic in nature when X less than or equal to 0.3, where X=[SDS]/[CTABr].