Although this volume is ostensibly devoted to diffusion per se, it also covers ionic conduction because this phenomenon, in the often complex and charge-sensitive structures of many ceramics, usually gives important clues as to the routes taken by all migrating species.The definition of what constitutes a ceramic is also liberally interpreted here so as to include substances which are not normally used as such in the industrial sense. One obvious anomaly is the class of so-called room-temperature superconductors which, perversely, are expected to be used at the opposite end of the temperature scale to traditional ceramic applications. The coverage of research on oxides, carbides and nitrides herein is believed to be as complete as possible, while other possible candidates for inclusion are not necessarily to be found in the 'miscellaneous' section. Silicides, in particular, are notable by their absence.