In spite of substantial efforts by many investigators as well as numerous publications on the subject, the nomenclature of the systemic vasculitides remains enigmatic. A major problem is the lack of standardized diagnostic terms and definitions. Thus, different names are being used for the same disease and the same name is being used for different diseases. In an attempt to address this problem, an ad hoc committee of clinicians and pathologists from 6 countries and multiple medical disciplines convened in Chapel Hill, North Carolina, for the Chapel Hill Con-