Proton-coupled electron transfer (PCET) is an important mechanism for charge transfer in a wide variety of systems including biology- and materials-oriented venues. We review several areas where the transfer of an electron and proton is tightly coupled and discuss model systems that can provide an experimental basis for a test of PCET theory. In a PCET reaction, the electron and proton may transfer consecutively (ET/PT) or concertedly (ETPT). The distinction between these processes is formulated, and rate-constant expressions for the two reaction channels are presented. Methods for the evaluation of these rate constants are discussed that are based on dielectric continuum theory. Electron donor hydrogen-bonded-interface electron acceptor systems displaying PCET reactivity are presented, and the rate-constant expressions corresponding to the ETPT and ET/PT channels for several model reaction complexes are evaluated.