Vasculitis is a process that results from the inflammation of blood vessels and can occur de novo or secondary to a variety of diseases or drugs. Clinical presentation depends on the size and distribution of vessels involved. Anti-neutrophil cytoplasmic antibodies (ANCA) have been shown to have variable sensitivity in making the diagnosis of specific vasculitic syndromes, therefore histological confirmation may be necessary. Angiography is a useful tool in evaluating disease of large and medium-sized vessels that are inaccessible or potentially dangerous to biopsy. New imaging modalities are becoming more useful in diagnosing vessel wall changes, particularly in large-vessel vasculitides. In clinical practice it is not always possible to classify or apply a specific label to a patient with vasculitis, but for appropriate patient management it is important to define the extent and severity of disease and to exclude underlying secondary causes.