The term vasculitis embraces a heterogeneous group of conditions which may occur as primary phenomena or secondary to disorders such as rheumatoid arthritis or systemic lupus erythematosus. Classification of vasculitis is often difficult in the absence of identifiable aetiological factors or specific serological markers. However, the primary systemic vasculitides can be segregated morphologically, according to the size of blood vessels involved and the presence of granulomata (Table 1). Recently, the discovery of circulating antineutrophil cytoplasmic antibodies (ANCA) in many patients with these disorders, whose differing specificities substantiate the histological classification, has led to interest being focused on their relevance in the development of vasculitis. This paper reviews the historical aspects of the detection of ANCA, and the value of these antibodies in the diagnosis and management of the primary systemic vasculitides likely to be encountered by the dermatologist. The clinical features in patients with these vasculitides are also outlined.