The mechanism of the reduction of alpha- and beta-PbO2 electrodes has been studied using an all-solid-state system. PbO2 samples were prepared by electroformation of cured plates. HSbO3 . xH(2)O was used as the solid electrolyte. Galvanostatic discharge and Coulometric measurements were carried out at room temperature. The capacity was determined by integration of I-t curves and the number of electrons was calculated using Faraday＇s law. The electrochemical reduction of both alpha- and beta-PbO2 proceeds in two stages. The results show that the electrochemical reduction of both alpha- and beta-PbO2 takes place in the gel zones according to a proton-electron mechanism. (C) 2000 Elsevier Science B.V. All rights reserved.