Vasculitis underlies most of the characteristic lesions of Behçet's disease and is obligatory for the diagnosis in populations at risk. Sporadic cases and similar presentations in non-Silk-Route patients should be labelled as Behçet's syndrome and carry different prognosis because of differences in underlying pathologic changes and pathogenesis. Ethnicity and vasculitis should be included in diagnostic criteria. Large vessel involvement is characteristic if less common.