The purpose of Calpain Methods and Protocols is quite straightf- ward: it is to present the actual experimental methods used in many different laboratories for the study of calpain. It will provide the vital experimental detail, and the discussion of possible pitfalls, for which the standard journals no longer provide space. This will make it as easy as possible for investi- tors interested in calpain to adopt established methods without repeating old mistakes, and to adapt and apply these methods in novel approaches to the many outstanding calpain questions. These questions range from purely biochemical problems of protein structure and enzyme regulation at the molecular level, through large areas of cell biology, to applied and clinical aspects of calpain function in human d- ease. Within this panoply of topics, a wide range of investigators will find many fascinating and as yet unanswered questions about calpain. Calpain Methods and Protocols will provide instant access to many essential te- niques, while saving them the time and effort involved in developing a new method. In addition to questions relating to the normal physiological roles of the calpains, there is considerable evidence that inappropriate calpain activity may have pathological effects in many tissues, for example, following ischemia. This provides a major stimulus for the development of specific calpain inhi- tors for therapeutic purposes, and for the development of methods to evaluate such inhibitors.