Allergic granulomatosis and angiitis (Churg-Strauss syndrome) is characterized by a systemic vasculitis in the context of bronchial asthma and eosinophilia. Pathologically, there is a necrotizing vasculitis of small arteries and veins with extravascular granulomas, infiltration of vessels and perivascular tissue with eosinophilia. Pulmonary, peripheral nervous system, cardiovascular and cutaneous manifestations are most frequently encountered. Renal failure and high blood pressure are more rare. These features, within the setting of bronchial asthma and eosinophilia, differentiate Churg-Strauss syndrome from polyarteritis nodosa. Steroid associated to cyclophosphamide have considerably improved the prognosis and risk of relapse.