Vasculitis is caused by immune-mediated inflammation of blood vessel walls, resulting in tissue ischaemia, aneurysm formation, dissection and/or rupture. Diverse clinical presentations relate to distinct pathology and pathological mechanisms, size of affected vessels, pattern of organ and tissue involvement, and associated systemic inflammatory disease. The aetiology of most types of vasculitis is unknown, and all ages may be affected. Treatment is directed to known causes such as viruses and drugs, suppression of inflammation using corticosteroids and other immune suppressants, and, where indicated, revascularisation. Early recognition and institution of treatment enables prevention of permanent organ damage and has led to marked improvement in patient outcomes, with reduced mortality. Diagnosis is usually confirmed by biopsy of affected tissues, or imaging modalities when this is not practical. Adjunctive investigations of blood and urine are important to define specific subtypes of vasculitis, in order to determine the most appropriate treatment. Prevention and management of treatment side-effects including infection, osteoporosis, peptic ulceration, diabetes, hypertension, dyslipidaemia, and mood disorders, should be incorporated into routine care. Technological advances and collaborative research efforts underpin evolving concepts in the pathophysiology and principles of management of vasculitis.