Churg-Strauss syndrome (CSS) is a primary systemic vasculitis occurring primarily in patients with asthma. Unlike other small vessel vasculitides, CSS is characterised by blood and tissue eosinophilia. Corticosteroids are the therapy of first choice for all stages of the disease when active vasculitis needs to be treated rapidly. In patients with severe disease and organ- or life-threatening manifestation, the addition of cyclophosphamide appears to improve the outcome and reduces the incidence of relapses. In cases with an apparently better prognosis and less severe disease, methotrexate can be given as a corticosteroid-sparing agent in order to reduce the cumulative dose of corticosteroids, which is generally high in most cases as long-term administration of corticosteroids is often inevitable in order to control asthma, even if the vasculitis is inactive. In very severe cases of CSS, cyclophosphamide and corticosteroids may be insufficient to induce remission. In these cases, anti-TNF blocking agents such as infliximab or etanercept, may be added for a limited period of time. As this intense immunosuppression increases the risk for infections, a prophylaxis with sulfamethoxazole/trimethoprim is advised. Alternatively, the administration of recombinant IFN-alpha can be a effective when given on a short-term basis in otherwise refractory cases. Whether a continuous administration of immunosuppressive agents in addition to corticosteroids can reduce the frequency of relapses in CSS who are in remission is still unknown. As relapses occur in > 25% of all patients, studies addressing the prevention of relapses in CSS are highly desirable in the future.