A study has been made of the adsorbed products of H2S on a solid polymer electrolyte (SPE)-Pt electrode by electrochemical and XPS methods. The adsorbed products depend on the potential. On the basis of an investigation of the oxidation of hydrogen sulfide, a quantitative determination of H2S concentration in the gas phase was carried out on the SPE-based electrode system in a controlled potential mode. The electrode system has a number of attractive properties, including a low detection limit, good reproducibility, fast response and satisfactory linearity.