The desorption rate of surfactants ions from styrene / acrylamide copolymer latex par-ticles was investigated by applying the electric stopped-flow method at the concentration below the critical micell concentration. The surfactants used were sodium decyl, sodium dodecyl, sodium tetradecyl and sodium hexadecyl sulfates. The desorption rate constants were obtained by applying the first-order reaction scheme. The adsorption rate constants of those ions to the particles were estimated from the experimental desorption rate con-stants and adsorption equilibrium constants assuming the second-order kinetics. The de-sorption rate constants were determined to be 4 - 7sec-1 and the adsorption rate constants to be 3 X 104 - 2 X 105 mol - I dm3 sec - 1 ; the former decreased and the latter increased with increasing number of carbon atoms in alkyl chain of the surfactants.