We report a case of infected intracardiac hydatid cyst in a patient who had complaints of chest pain, exertional dyspnea, palpitation, evening fever and fatigue. Echocardiography demonstrated a left ventricular apical cystic mass-in 7 cm diameter. Magnetic resonance imaging and hemagglutination test confirmed the diagnosis. Single capsulated cyst full of pus was surgically removed by using cardio-pulmonary bypass. Histopathological examination revealed an infected hydatid cyst. Postoperative recovery was uneventful and the patient remains free of symptoms after one year of follow-up. (C) 2003 The International Society for Cardiovascular Surgery. Published by Elsevier Science Ltd. All rights reserved.