Treatment of cardiac dysfunction associated with Churg-Strauss syndrome (CSS) is empiric since the histologic findings provided by endomyocardial biopsy are rare and often nondiagnostic. Myocardial necrotizing vasculitis presenting as restrictive cardiomyopathy has not been reported before. A case of CSS, presenting with fever and progressive heart failure due to pericarditis, eosinophilic endomyocarditis, and myocardial necrotizing vasculitis, is reported. Cardiac involvement assessed by noninvasive (cardiac two-dimensional echocardiogram and nuclear magnetic resonance [NMR] imaging) and invasive (cardiac catheterization, angiography, and biopsy) studies showed a moderate degree of pericardial effusion and left ventricular (LV) dysfunction (ejection fraction 0.40), severe diastolic dysfunction (increased right and LV filling pressure with a dip and plateau pattern) and a severe reduction of cardiac index (1.6 L/min/m2). Histologic characteristics showed marked eosinophilic infiltration of the endocardium and myocardium with myocitolysis and fibrinoid necrosis of arterioles, venules, and capillaries. Combination therapy of steroids and cyclophosphamide resulted in both a clinical (regression of pericardial effusion, normalization of systolic and diastolic dysfunction, and increase of cardiac index to 2.8 L/min/m2) and histologic (sequential endomyocardial biopsies at 1, 3, and 6 months of follow-up) resolution of cardiac involvement. No recurrences were registered at 12-month follow-up with the patient receiving a maintenance drug regimen.