A critical review is presented of the available data of interface formation on cleaved III-V compound semiconductors which challenges unconfirmed structural assumptions that seriously affect spectroscopic interpretations. The results for GaAs indicate that many, if not most interfaces are probably abrupt for room-temperature formation. It is shown that the heat of condensation of Ag and Al is not sufficient to promote interactions at room temperature on most GaAs surfaces. For noble metals on GaAs defect formation does not appear to be a likely mechanism for Schottky barrier formation, and an alternative mechanism based on intrinsic adatom states is suggested. The available data of the oxidation of the GaAs(110) surface is reviewed. Further arguments of the involvement of Ga during the early stages of oxidation are given. Recent data for large oxygen exposures is reinterpreted in terms of both subsurface oxidation occurring prior to monolayer coverages, and oxygen coverages far exceeding a monolayer for extreme exposures. © 1983.