Cardiac echinococcosis has not been reported frequently. Because of the risk of potentially lethal complications, early diagnosis and definitive treatment are very important The case of a 41-year-old physician, in whom diagnosis of giant left ventricular hydatid cyst was established with cross-sectional echocardiography and magnetic resonance imaging, is presented. The cyst was removed surgically and mitral valve replacement performed because of destruction of the valve. © 1994, SAGE Publications. All rights reserved.