The surface composition of the H2SO4/H2O binary system in the temperature range (298-170 K) has been studied using differentially pumped Auger electron and X-ray photoelectron spectrometers designed to perform under equilibrium conditions (P-H2O approximate to 10(-6)-10(-4) Torr). Both spectroscopies have been calibrated on pure sulfuric acid solutions to illustrate their ability to provide accurate atomic stoichiometries within the nearsurface region. In the case of AES this ability has also been extended as a tool for the study of the surface composition in the H2SO4/H2O binary system under equilibrium conditions. Compositional analysis of this acidified surface indicates that under these experimental conditions the chemical compositions of the bulk and near-surface region are equal within,experimental error. Mass spectrometric analysis of the vapor composition indicates equilibration between the acid solution and D2O.