Surface characterization of Ir-based Ti-and Sn-containing electrodes of nominal composition, Ir0.3Ti(0.7-x)SnxO2 (0 less than or equal to x less than or equal to 0.7), was performed ex situ by scanning electron microscopy and energy-dispersive x-ray and in situ by open-circuit potential measurements and cyclic voltammetry. Despite the use of SnCl2 as precursor, energy-dispersive x-ray results showed the real composition to be very distinct from nominal due to SnCl4 volatilization during the calcination step in the electrode preparation procedure. SnCl4 formation in the precursor mixture was confirmed by visible spectrophotometric measurements. The substitution of TiO2 by SnO2 results in a significant increase in electrochemically active surface area, as supported by scanning electron microscopy, anodic voltammetric charge, q(a), and the double-layer capacity, C-dl, as a function of composition. Roughness factors between 3600 and 5100 were obtained. A linear C-dl vs. q(a) graph with an angular coefficient close to one was obtained.