ANCA-associated vasculitis represents a group of small-vessel vasculitides, including Wegener's granulomatosis, microscopic polyangiitis and the Churg-Strauss-syndrome. These diseases affect mainly small arteries, venules and capillaries, showing a lack of immunocomplex formation on immunohistology, the so-called "pauci-immune" vasculitis. Nevertheless, Anti-Neutrophil Cytoplasmatic Autoantibodies (ANCA's) are pathogenic for this type of disease. In spite of important advances in technical diagnostic tools, careful medical history and clinical examinations often give the clues for the correct diagnosis. Recent collaborative therapeutic studies have lead to therapeutic schemas that are much more adapted to the individual disease state. Besides the acute and sometimes life-threatening form of ANCA-vasculitis, chronic disease and relapses become more important in clinical practice. Thus, therapeutic efficacy must be outweighed against long-term toxicity to make the right choice for therapeutic intervention in ANCA-associated vasculitis.