Charge transport through a Nafion(R) membrane incorporating dispersed Ru(bpy)(3)(2+) (bpy = 2,2’-bipyridine) complex has been investigated by in-situ spectrocyclic voltammetry (SCV) measurements. The ratio R(CT) of the electrochemically active complexes was obtained from the visible absorption spectral change; it increased with increasing the complex concentration c in the membrane. The distribution of the intermolecular distance was taken into account using a statistical calculation. The relationship between R(CT) and c was derived on the basis of the center-to-center distance distribution between the nearest-neighbor molecules, and the value of the charge transfer distance R(0) was obtained from this relation using a charge-hopping model. The R(0) value depended on the scan rate of the potential. At high scan rates, at which bounded motion of the complex is almost negligible, R(0) = 0.93 nm was taken as the charge-hopping distance between adjacent redox centers. The R(0) value at slow scan rates (e.g. R(0) = 1.5 nm at 2 mV s(-1)) includes charge hopping between adjacent redox centers as well as the bounded motion of the complex.