The electronic densities of occupied states at Si and Pt atoms at the Pt/Si(111) interface are monitored through the Si(Li23VV) and Pt(N7OO) Auger electron spectra. These are sensitive to the local densities of occupied states in the valence band, and thus to the local atomic geometry. Different morphologies of the interface are studied, with distinguishable spectra: (i) growth of a layer of Pt, uniformly covering the Si(111) surface, (ii) a mixed interface with instant penetration and reaction during deposition, and (iii) an annealed, √3 × √3 superstructure with approximately a third of a monolayer of Pt. The true lineshapes, corrected for inelastic energy losses, are derived by a novel deconvolution technique. Spectra of PtSi Si(L23VV) and Pt(N7OO)) directly indicate strong Si-Pt hybridization and a lowering of the density of states at the Fermi level, compared to clean Pt. The concept of a critical thickness of metal for the break-up of the Si bonds at the surface is corroborated by this study.