The Churg Strauss Syndrome is an eosinophil-associated small vessel vasculitis. Although its pathogenesis may be distinctive and the association with severe late-onset asthma typical, the clinical features during the vasculitic phase widely overlap with those of the other forms of necrotizing vasculitis, and no single clinical or histologic feature is pathognomic of the condition. Renal involvement is common, although usually mild, and even when severe it tends to respond well to treatment. The prognosis for both patient and renal survival with adequate treatment is in general good. The optimal treatment strategy, however, is uncertain, and may differ from that for the other vasculitides. In particular, in contrast to Wegener's granulomatosis, the need for routine cyclophosphamide treatment is unconfirmed and requires further study.