The early stages in the formation of the InP(110)-oxide interface have been studied using high energy resolution photoemission with synchrotron radiation. Both unexcited and excited oxygen were used. Changes were observed in P 2p, In 4d and valence-band spectra. The oxidation of InP appears spatially inhomogeneous. Three stages were observed: a precursor chemisorption stage, a nucleation process, the formation of an oxide layer. © 1986.