In recent years a growing number of proteases have been identified that catalyse peptide bond hydrolysis in the plane of the cellular membrane. These so-called intramembrane-cleaving proteases (I-CLiPs) are involved in a diverse range of cellular processes, including cell regulation, signalling, quorum sensing, protein processing, lipid metabolism and the unfolded protein response. Some I-CLiPs play critical roles in diseases such as Alzheimer s and viral infection. The authors, who are all world leaders in this exciting field of cell biology, provide an overview of the various proteases including recent data derived from the structural determination of some of the I-CliPs, and discuss the various roles that these proteases play in biology and disease. The aim of this book is to provide an update on this emerging group of unusual but important proteases for both the specialist and those with a broader interest in proteases. Amongst the target audience will be protease researchers, enzymologists, those working in academia and the pharmaceutical industry on biological processes and diseases involving I-CLiPs.