This paper describes electrocatalytic properties of composite films containing Pt microparticles dispersed in W(VI,V) oxide supports. The coatings were prepared electrochemically on graphite. Their behavior in 2 M H 2SO 4 is not a simple sum of the properties of the components. Even at low Pt levels in the coatings, the overpotential for hydrogen evolution is decreased by almost 500 mV compared to that at bare graphite. Although the catalytic effect is related to the presence of finely dispersed Pt, the interaction of the particles with the hydrogen tungsten oxide bronzes, which develop in the support, presumably weakens Pt-H bonds and favors hydrogen desorption. At moderate Pt loadings, the voltammetric reduction of oxygen begins at the most favorable potential available on Pt (0.5 V vs. SCE), and the ring-disk voltammetry does not show H 2O 2, as an intermediate or product. To utilize all of the three-dimensionally distributed Pt centers, the W(VI,V) oxide must be reduced partially, a condition that makes it highly reactive and non-blocking to protons and electrons. The activity of platinum for the voltammetric oxidation of methanol was enhanced by reductive conditioning at −0.2 V vs. SCE, where hydrogen spillover from Pt to yield hydrogen tungsten bronzes takes place. The latter process is believed to be responsible for the removal of passivating methanol residues, presumably by desorptive hydrogenation. At low ratios of Pt to W(VI,V) oxide, the system exhibits a notable catalytic reduction of otherwise highly irreversible chlorate.