The effect of polyvinylsulfate (PVS) on the photoinitiated electron transfer reaction from the lowest charge transfer state of Ru(bpy)32+* to Fe(III) and on its dark back reaction was studied under various conditions. A large acceleration of both reactions was observed which can be attributed to concentrating both reacting cations into the field of the polyelectrolyte. However, for the electron transfer from Ru(bpy)32+* to Fe(III), the rate constant (normalized for the concentrating "volume effect") was found to increase linearly with the concentration of Fe(III) per polymer molecule up to 25% coverage. Fe(III) complexes with the sulfate groups of PVS, and it seems certain that the increase in the rate constant has its origin in the bonding or chelating of the Fe(III). Possible explanations of the increase are discussed. At high coverage of the polymer by Fe(III) the rate constant starts to drop, most probably due to configurational changes of the polymer induced by the cations. The initial yield of the electron transfer remains unchanged by the addition of PVS while the back reaction was greatly enhanced. In cases where an average of one or less pairs of products were produced per polymer chain a large contribution to the back reaction from a first-order rate law could be observed. As the number of product pairs per polymer molecule increased the dominant portion of this reaction followed a second-order rate law.