The polymerization of aniline was electrochemically performed on RuO2 and Pt electrodes in 0.5M H2SO4 using cyclic voltammetry. The results showed that the rate of aniline polymerization was strongly dependent upon the upper anodic potential limits of cyclic voltammetry as well as upon the type of anodic substrates employed. In comparison to polymerization rates of aniline on a RuO2 electrode, those on a Pt electrode were higher and lower for cyclic voltammetric scans of -0.2 to 0.8 V and -0.2 to 1.2 V, respectively The results of X-ray photoelectron spectroscopy (XPS) showed that the aniline degradation products easily form during polymer growth, at -0.2 to 1.2 V.