Many cutaneous and systemic disorders are associated with inflammation and necrosis of blood vessels. Several classifications of vasculitis have been used. Internists tend to utilize the classification of Fauci with modifications such as those by Cupps. Gibson and Ryan, who are dermatopathologists, have classified vasculitis based on vessel size, leukocyte type, and presence of granulomas. A more recent classification has been developed by Jennette, a pathologist, and colleagues. The etiology of vasculitis is varied; it includes bacteria, viruses, chemicals, autoimmune disease, malignancy and abnormal exogenous and endogenous proteins. Leukocytoclastic vasculitis can be experimentally reproduced by the Arthus phenomenon. IgM and C3 are found in cutaneous blood vessels and associated with circulating immune complexes. CH50, C3 and C4 may be reduced in serum. Increased incidence of nasal carriage of staphylococci is associated with higher relapse rates in Wegener's granulomatosis and toxic shock syndrome toxin from staphylococci is associated with the Kawasaki syndrome. Additionally, at least four systemic vasculitic drug reactions can be confirmed with patch testing. Antineutrophil cytoplasmic antibodies (ANCA) are found in association with certain systemic vasculitides. These may be tested with indirect immunofluorescence and enzyme linked immunosorbent assays (ELISA) with radioimmunoassays. Originally cytoplasmic ANCA (cANCA) was identified with proteinase 3 as the antigen and perinuclear ANCA (pANCA) was related to myeloperoxidase. While cANCA is very specific for proteinase 3, pANCA is associated with a number of antigens other than myeloperoxidase. pANCA is found with alcohol fixed but not formalin-fixed neutrophils. cANCA is particularly sensitive and specific for Wegener's granulomatosis and predicts prognosis and response to therapy. pANCA is not so specific and is associated with a number of other vasculitic syndromes. Cutaneous vasculitis is managed primarily with colchicine, dapsone and prednisone, with recent studies indicating that there may be a synergistic effect of pentoxifylline with dapsone. Systemic vasculitis involves treatment with various agents. Recently it has been observed that co-trimoxazole (trimethoprim/sulfamethoxazole) is useful in many cases of Wegener's granulomatosis along with other more toxic chemotherapeutic agents.