The electronic structure of the silver chalcogenide compound Ag2S has been investigated, experimentally using photoelectron spectroscopy, and theoretically using the full-potential LMTO calculation. The photoemission data taken using a synchrotron photon source is compared with the calculated valence density of states' (DOS). The band structure is also calculated for the high-temperature cubic disorder phase. For that sake, a hypothetical ordered structure model is utilized instead of the disorder structure. From the hitherto reported crystallographic data and the calculated total energies, microscopic mechanisms of the phase transition and superionic conduction are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.