The temperature dependence of a charge transport rate, nu(CT) (mol dm(-3) s(-1)) in a Nafion(R) membrane incorporating a trinuclear ruthenium complex, Ru-red ([(NH3)(5)Ru-O-Ru(NH3)(4)-O-Ru(NH3)(5)](6+)) was studied using potential-step chronocoulospectrometry (PSCCS). The nu(CT) increased with increasing complex concentration and temperature. It was found from the analysis of the nu(CT) that the charge transport takes place by both physical displacement and charge hopping, and the first-order rate constant (k(1) (s(-1))) for the physical displacement and the second-order rate constant (k(2) (mol(-1) dm(3) s(-1))) for the charge hopping were obtained. The k(2) increased by one order of magnitude for a temperature increase from 5 to 35 degrees C, but k(1) increased only by a factor of 1.6. Both the physical displacement and charge hopping in the membrane are of the Arrhenius type, and the activation energy, E-a (55 +/-11 kJ mol(-1)), for the charge hopping was much larger than that (13 +/- 5 kJ mol(-1)) for the physical displacement. It was suggested from the discussion on the other activation parameters that the physical displacement is entropy-controlled, but the charge hopping is enthalpy-controlled at room temperature.