The electrooxidation of primary alcohols with four to eight carbon atoms on black Pt electrodeposits on gold/quartz, and on commercial bright platinum/quartz electrodes in perchloric acid solution, was studied by cyclic voltammetry (CV) and with the electrochemical quartz crystal microbalance (EQCM). Alcohol physisorption and Pt oxide reduction by chemical reaction with the alcohols were observed, both processes increasing with increasing chain length of the alcohol. Hexanol addition at 0.4 V versus SCE, the potential at which Pt oxidation starts, or higher potentials produced both an anodic current of hexanol electrooxidation and a mass decrease of bright Pt/Q electrodes, which shows unequivocally that the alcohol reduces the Pt oxide chemically.