The redox reaction between bromate and bromide ions in aqueous acid medium was studied in the absence and presence of cationic and anionic surfactants. The rate equation in water was found to be v = k(3)(w)[BrO3-][Br-][H+](2). The cationic surfactant, tetradecyltrimethylammonium bromide, catalyzes the reaction, using either HBr or HNO3 as the source of H+; nevertheless, the observed rate constant decreases slightly, goes through a minimum, and increases again as the tetradecyltrimethylammonium nitrate concentration increases. The anionic surfactant, sodium dodecyl sulfate, strongly inhibits the reaction when its concentration is increased, reaching a leveling off at high surfactant concentration; but hydrogen dodecyl sulfate catalyzes the reaction. These micellar effects are quantitatively explained on the basis of the pseudophase ion exchange model : tetradecyltrimethylammonium bromide increases the Br concentration, while sodium dodecyl sulfate decreases the H+ concentration (through the exchange with Na+ counterions) in the water phase where the reaction takes place.