Interfacial reactions between (100) InP and thin films of the transition metals Cr, Ni, Pt, and Ti have been studied. A thin layer of metal was deposited onto the InP substrates using e-beam evaporation and parts of the samples were then subjected to heat treatment in vacuum for 30 min at several temperatures up to 500 °C. Separate characterizations of the metal, In, and P depth distributions were carried out using mass and energy dispersive recoil spectrometry. The different crystalline phases observed were determined using x-ray diffraction. The near-noble metals (Ni, Pt) formed ternary phases, while Ti and Cr formed phosphides. The phases formed were generally stable up to 500 °C with the major exception being Pt where the ternary phase decomposed to form PtIn2, PtP2, and Pt3In7.