Churg-Strauss syndrome (CSS) is a rare necrotizing small-vessel vasculitis associated with eosinophil-rich granulomatous inflammation of tissues and vessels and is also associated with asthma and eosinophilia. Epidemiologic studies continue to show that CSS is the rarest of the necrotizing small-vessel vasculitides. However, it is not possible to know with any certainty if there has been an increase in incidence. There has been an attempt to divide the patients with CSS into an antineutrophil cytoplasmic antibody-positive and cytoplasmic antibody-negative group. The former group has an increased frequency of renal involvement, parenchymal pulmonary disease, constitutional symptoms, and peripheral and central nervous system involvement, whereas the latter group has more frequent cardiac disease. The role of eosinophils and antineutrophil cytoplasmic antibodies remains poorly defined but provocative. Leukotriene receptor antagonists do not appear to induce CSS but facilitate the tapering of glucocorticoids, which unmasks the condition. Glucocorticoids and cyclophosphamide remain the foundation of treatment for vasculitis, but there are other promising and less toxic alternatives on the horizon.