This volume is the first to combine latest information on viral, microbial and cellular proteolytic enzymes as potential targets for human therapeutics. Proteases control a large array of physiological reactions, and are involved in a variety of pathological processes for which effective medications are currently needed and/or being sought after. Although protease inhibitors have been investigated for many years, few have been employed therapeutically. Recent break- through by HIV protease inhibitors as therapeutic drugs has re-encouraged the search for inhibitors of other proteolytic enzymes. Klaus von der Helm, who described the first viral protease has brought leading experts together to discuss not only the success and problems of clinical use and continuing prospects, but to review further potential drug targets. This volume provides detailed information and evaluations of key viral, bacterial, fungal, and cellular proteases as potential future drug candidates.