A case of hypereosinophilic syndrome (HES) initially manifesting as endomyocardial disease in a 21-year-old man is presented. The diagnosis of HES was made according to the Chusid's criteria. Myeloproliferative disorders were excluded and corticosteroid therapy with prednisone at a dose of 1 mg/kg/d was started immediately. After 30 days of continuous corticotherapy the patient recovered completely. His blood eosinophil count decreased from 8740 cells/microL (48.7%) to 30 cells/microL (0.3%). Then, prednisone was discontinued gradually. During 18-month follow-up the patient was free from cardiovascular symptoms and his complete blood count was normal. We also present the current state of knowledge on the cardiovascular complications of hypereosinophilic syndrome.