The oxidation of hydrogen gas in aqueous solution by oxidants such as H2O2, Na2O2, K2Cr2O7, CrO3 + H2O, ClO2-, and ClO3- + Cl- has been found to take place in an oscillatory manner on the surface of platinum. Oscillations in the resting potential of a Pt electrode were observed without applying external voltage or current. The primary cause of the oscillations is not related to the cations or anions added to the solution. The dependence of the oscillatory behavior on the concentration of the oxidants and on the type of acid in the supporting electrolyte, the effect of added halide ions on the oscillations, and the behavior of other noble metal surfaces in the hydrogen-oxidant systems have been studied. The heterogeneous (gas-solid-liquid) H-2-(Pt)-oxidant oscillators seem to represent a link between the oscillatory heterogeneous catalytic surface (solid-gas) reactions and the oscillatory electrochemical (solid-liquid) reactions.