The instability of the commonly adopted support (e.g., Ti, Ti-Pd alloys, Ta) for the preparation and characterization of different electrode materials has been overcome by depositing the electrode material of interest (RuO2) on conductive, boron-doped diamond (BDD). The present paper reports results on the model chlorine evolution reaction, investigated at BDD surfaces modified by RuO2 loadings of 1.2 x 10(13), 6.0 x 10(14), and 2.65 x 10(16) molecules cm(-2). A radical spillover mechanism is proposed for the reaction occurring at the electrode having the lowest noble-metal oxide loading.