Stimulated oxidation of InP (100) surfaces by primary electron beams was studied by Auger electron spectroscopy. At the point of impact of the incident beam, we concluded that the formation of indium oxide and of a volatile phosphorus oxide occur, which explains the phosphorus depletion of the first monolayers. The low‐energy electron‐diffraction patterns for successive heat treatments and electron‐stimulated oxidations of InP surfaces, and the corresponding characteristic‐energy‐loss spectra were performed. For heat treatments close to the decomposition temperature, we report here on how low‐energy‐loss spectroscopy was used to supply the deficiency of Auger electron spectroscopy, the latter method being unable to detect the formation of indium microdroplets.