A simplified 5-RC transmission line equivalent circuit was introduced. Manganese dioxide cathodes from three commercial primary alkaline cells were investigated by means of ac impedance technique. Cathode Ohmic resistance, Faraday resistance for the reduction of MnO2, proton diffusion rate inside the lattice of EMD and electrochemical accessible surface area were obtained by numerical fitting of impedance data using the simplified transmission line model. The kinetics for cathode surface accessibility was also studied.