The vasculitides are a heterogeneous group of disorders that can range from mild inflammation of blood vessels in the skin, to organ- and life-threatening diseases. The term ‘vasculitis’ is a pathological description of blood vessel wall inflammation which leads to ischaemia and infarction of the target organs. Definitions and classifications of the primary vasculitides are mainly based on the predominant calibre of the blood vessels involved but incorporate clinical, pathological, and laboratory features. The secondary vasculitides usually occur in the context of other connective tissue diseases and are not discussed further in this section. Goodpasture’s disease is not usually included in the primary vasculitides, but has compatible clinical features of pulmonary capillaritis and glomerulonephritis.