Especially the past two decades have seen renewed interest in the vasc ulitides. In this volume an international expert group presents the cu rrent state of knowledge and concentrates on principles of immune modu lating therapy. Drawing from their work in rheumatology, nephrology, i nternal medicine, connective tissue disease and clinical immunology, t hey present new concepts in classificiation, diagnosis and pathophysio logy of the vasculitides. Evidence from experimental and clinical tria ls is reviewed, as well as the outlook for further research.