Proton exchange membrane fuel cells (PEMFCs) are an exciting clean energy technology for power delivery for a range of devices from automotive applications through to portable digital equipment. Current technology for PEMFCs is limited by its inability to operate at high temperatures which is particularly desirable for automotive applications. This review summarises and discusses the key areas of research in recent years for non-polymer based high temperature membranes or so-called solid acid membranes. The review addresses: the reasons for operating at high temperatures, the proton transport mechanisms, the limitations of current polymer membranes and their modification and on the future of solid acid membranes elaborating on future pathways which may bring about tangible enhancements in this technology. (c) 2004 Elsevier B.V. All rights reserved.