Churg-Strauss syndrome is a systemic and pulmonary vasculitis, defined by its association with severe asthma and with hypereosinophilia of the blood and tissues. The systemic vasculitis is a small-vessel vasculitis frequently associated with purpura, mononeuritis multiplex, and, more rarely, with rapidly progressive glomerulonephritis or diffuse alveolar hemorrhage. Its prevalence of 7 to 13 per million population makes it one of the rarest of the systemic vasculitides. Anti-MPO (antimyeloperoxydase) pANCA (ANCA with a perinuclear fluorescence pattern) are present in 35-40% of cases and appear to determine a subgroup of patients with a higher frequency of renal damage, alveolar hemorrhage, and central nervous system involvement. The diagnosis of Churg-Strauss syndrome is made on the basis of clinical features. In patients with late onset asthma the presence of constitutional symptoms, eosinophilia (> 1000/mm3), the appearance of a systemic illness characterized by monoreutis multiplex, purpura, cardiomyopathy or pulmonary infiltrates should lead to consider the diagnosis of Churg-Strauss syndrome. Cardiac involvement is an important cause of morbidity and the leading cause of specific mortality in Churg-Strauss syndrome. Treatment is based on corticosteroid therapy and immunosuppressive drugs (cyclophosphamide and azathioprine) and is determined according to validated prognostic criteria (Five Factors Score). Complete remission occurs in almost 90% of cases, and the 10-year survival rate has reached 79.4%. Relapses are frequent (25% of cases) and even after recovery from vasculitis, most patients (90%) still have asthma requiring corticosteroid treatment.