The effects of sodium dodecyl sulfate, SDS, micelles on the reaction between a number of arenediazonium, ArN2+, ions with hydrophilic L-ascorbic acid or vitamin C, VC, and the hydrophobic analogue 6-O-palmitoyl-L-ascorbic acid, VC16, have been investigated at different pH values. Previous results indicate that in aqueous acid solution, in the absence of surfactant, the reaction between ArN2+ and VC takes place through the rate-limiting decomposition of a diazo ether "complex" formed from the interaction of ArN2+ with the monoanion form of ascorbic acid, VC-, in a rapid pre-equilibrium step. The kinetic profiles found for the reaction of ArN2+ with VC or with VC16 together with high-performance liquid chromatography data suggest that the presence of SDS micelles does not alter the reaction pathway. Addition of SDS decreases the observed rate constant, k(obs), for the reaction with VC up to a minimum after which further addition of SDS leads to a slight increase in k(obs). The k(obs) values at the minimum are significantly above zero and much higher than those for the spontaneous thermal decomposition of ArN2+, suggesting that at high [SDS], a fraction of VC- ions are present in the micellar Stern layer. At high [SDS] = 0.8 M, saturation kinetics is observed for the reaction with VC 16 upon increasing [VC16], but at moderate [SDS] = 0.16 M only the initial linear regions of the saturation profile are observed. The reaction is, however, inhibited upon increasing [SDS] at any fixed [VC16], with k(obs) approaching the value for the thermal decomposition of ArN2+. Results with VC and VC16 are consistent with the pseudophase model and are rationalized in terms of the electrostatic micellar-induced separation of reactants and co-ion (VC-) incorporation into the micellar Stern layer and by assuming that the local VC16 concentration in the micellar pseudophase decreases because of the dilution effect caused by increasing [SDS] (VC16).