This work presents electrochemical studies of ceria as an electrode material and describes new possibilities of exploring the unique catalytic and redox properties of this material for the development of a simple enzymeless sensor for the determination of H2O2 and for biosensor manufacturing. The investigation of the electrocatalytic activity of ceria toward the oxidation and reduction of hydrogen peroxide was first carried out using cyclic voltammetry in alkaline and neutral conditions. A possible reaction mechanism was suggested involving different cerium oxidation states and reactive species. The ceria-based sensor resulted in rapid, sensitive, and accurate measurement of H2O2, with a response time of less than 10 s, a detection limit of 98 nM, and a sensitivity of 0.24 mu A mu M-1. This material provided a biocompatible matrix for the immobilization of glucose oxidase and facilitated direct electron transfer between its active center and the electrode surface, with an electron-transfer rate constant of 18.3 s(-1) and a surface coverage of 1.4x10(-11) mol/cm(2). This study introduces ceria as electrode material for sensing and biosensing applications. (C) 2008 The Electrochemical Society.