Cardiac involvement frequently occurs in hypereosinophilic syndrome. The endocardium seems to be most susceptible to disturbances deriving from eosinophilia as seen in Loeffler's endocarditis. Hypereosinophilia and cardiac involvement are also seen in Churg-Strauss syndrome. The present report deals with a patient with Churg-Strauss syndrome who exhibited marked endomyocardial fibrosis that was visualized by cardiac magnetic resonance imaging. Loeffler's endocarditis is the classical endocardial manifestation of hypereosinophilic syndrome. Similarities between Loeffler and Churg-Strauss syndromes had been described previously. Potentially, endocardial involvement is more common even in Churg-Strauss syndrome than expected so far. The significance of these findings remains to be shown.