Semiconductor nanowires of III–V materials have generated much interest in recent years. However, the growth mechanisms by which these structures form are not well understood. The so-called vapor–liquid–solid (VLS) mechanism has often been proposed for III–V systems, with a chemically inert, liquid metal particle (typically Au) acting as a physical catalyst. We assert here that Au is, in fact, not inert with respect to the semiconductor material but rather interacts with it to form a variety of intermetallic compounds. Moreover, we suggest that III–V nanowire growth can best be understood if the metallic particle is not a liquid, but a solid-phase solution or compound containing Au and the group III material. The four materials GaP, GaAs, InP, and InAs will be considered, and growth behavior related to their particular temperature-dependent interaction with Au.