Preliminary passivation studies established that kinetic measurements could be made at α- and β-lead dioxide electrodes, in perchloric acid electrolytes, without the intrusion of solid films. The kinetics of the rate controlling exchange reaction at α- and β-PbO2 have been investigated using the galvanostatic pulse technique. The overpotential-current density data was interpreted in terms of two rate controlling charge transfer mechanisms. Around the equilibrium potential the reaction mechanism appears as a simultaneous two-electron transfer which changed to two consecutive single-electron transfer steps at high overpotential. Possible reaction mechanisms have been discussed on the basis of the observed kinetic parameters. Differential capacitance-potential data for α- and β-PbO2 has been measured in inert electrolytes. A comparison of the electrochemical behaviour of α- and β-PbO2 has been made.