{Thin films made from compound semiconductors, such as indium phosphide, gallium arsenide and their alloys, have key applications in electronic and photonic devices. These single-crystal materials are fabricated by metalorganic vapor-phase epitaxy (MOVPE). In our laboratory, an ultra-high vacuum system has been connected to a state-of-the-art MOVPE reactor so that the semiconductor surfaces may be characterized in the growth environment. The atomic composition and structure of these materials has been determined by scanning tunneling microscopy, infrared spectroscopy, reflectance difference spectroscopy, x-ray photoelectron spectroscopy, and ab initio molecular cluster calculations. It has been found that indium phosphide and gallium arsenide exhibit very different surface structures under MOVPE process conditions. A disordered double-layer of As atoms with a few alkyl radicals are adsorbed on GaAs (001), while on InP (001), the surface is terminated with H atoms adsorbed on P dimers. This latter structure exhibits a single-domain (2x1) reconstruction. Another interesting example of III/V semiconductor surface chemistry is the formation of InGaAs/InP interfaces. Localized strain produces atomic arrangements that are distinct combinations of InP and InAs reconstructions. The application of this knowledge to the growth of epitaxial device structures will be discussed. @FootnoteText@ invited by David Castner.}