Salt and solvent effects on the kinetics of the reactions [Fe(CN)(6)](3-) + [Ru(NH3)(5)pz](2+) reversible arrow [Fe(CN)(6)](4-) + [Ru(NH3)(5)pz](3+) (pz = pyrazine) have been studied through T-jump measurements. The forward and reverse reactions show different behaviors: "abnormal" salt and solvent effects in the first case and normal effects in the second one. These facts imply an asymmetric behavior of anion/cation reactions depending on the charge of the oxidant. The results can be rationalized by using the Marcus-Hush treatment for electron-transfer reactions.