Churg-Strauss syndrome (CSS) is a rare systemic vasculitis of the small- and medium-size vessels. It is mostly seen in elderly patients presenting as de novo asthma, eosinophilia, and vasculitic organ involvement. In childhood, CSS is extremely rare. The course of pediatric CSS is usually severe and often lethal. We present a case of a 13-year-old girl with a short history of asthma, marked eosinophilia, and multiorgan involvement. The extremely high level of blood eosinophilic granulocytes (51.6 × 10(9)/L) prompted a workup for eosinophilic leukemia before the diagnosis CSS could be made. Subsequently, the disease was successfully treated. This case report shows a classical case of childhood CSS, remarkable because of the presence of extreme hypereosinophilia. It underlines the importance of CSS as a life-threatening cause of hypereosinophilia in children.