We report new photoemission studies of the Au–InP (110) interface for both n- and p-type samples using synchrotron radiation in the energy range 80 to185 eV. By slowly increasing Au coverages and by studying core level structures and valence band spectra we have been able to differentiate between two coverage intervals. The lower coverage interval (θ<1 ML) is dominated by band bending with no measurable chemical changes and with a total measured Schottky barrier height of 0.6 eV. In the higher coverage interval (1<θ≤37 ML), we observed changes in the In 4d and P 2p core level shapes and a monotonic shift of the Au 4f to lower binding energies with increased Au coverage. Evidence of intermixing of Au with the P and In atoms indicates the formation of a nonabrupt interface. These results are at variance with the view that Au is a nonreactive metal on InP (110).