Eosinophilic myocarditis is a rare form of myocarditis that is characterized pathologically by myocardial inflammation with eosinophils, often in association with elevated levels of circulating blood eosinophils. Eosinophilic myocarditis can be classified according to the presumed etiology (eg, hypersensitivity/allergic), associated clinical conditions, or abnormalities found on endomyocardial biopsy or at autopsy. There is overlap in the clinical features and pathologic findings among these different disorders, reflecting our incomplete understanding of the etiology and pathogenesis of the different forms of eosinophilic heart disease.