Kinetic studies of the reactions of [Ru(NH3)(5)pz](2+) (pz = pyrazine) with S2O82- and [Co(C2O4)(3)](3-) have been carried out in micellar solutions of sodium bis(2-ethylhexyl) sulfosuccinate. The results were analyzed using the pseudophase model. The binding constant of the ruthenium complex depends on the charge of the coreactant (S2O82- or [Co(C2O4)(3)](3-)) and, for a given coreactant, on its concentration. The results are explained taking into account: (i) the association ruthenium complex/coreactant in the aqueous pseudophase, (ii) the stabilization of the ruthenium complex in this pseudophase as a consequence of the ionic strength, and (iii) the reduction of the (effective) charge of the micelles when the concentration of (Na+) counterions is increased.