IrO2 electrocatalysts were prepared and electrochemically characterized for the oxygen evolution reaction in a Solid Polymer Electrolyte (SPE) electrolyzer. By using a sulfite complex-based preparation procedure, an amorphous iridium oxide precursor was obtained at 80 degrees C, which was, successively, calcined at different temperatures: 350 degrees C, 400 degrees C and 450 degrees C. A physico-chemical characterization was carried out by X Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray-photoelectron spectroscopy (XPS). The various IrO2 catalysts were sprayed onto a Nafion 115 membrane with a loading of 2.5 mg cm(-2) to form the anode. A Pt/C catalyst (Pt loading 0.5 mg cm-2) was used as cathode. The best electrochemical performance was obtained for the cell based on the IrO2 calcined at 350 degrees C. The maximum current density at high potentials (1.8 V) was about 1.75 A cm-2. Accelerated time-tests at 2 A cm-2 demonstrated a suitable stability of the IrO2 calcined at 350 degrees C; however, the intrinsic stability appeared to increase with the calcination temperature. The sample calcined at 400 degrees C could represent a good compromise between performance and intrinsic stability. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.