Although echinococcus is endemic in many sheep-raising areas of the world, cardiac involvement is rare. Cysts usually reach the heart by means of the coronary circulation, but other routes have been proposed. Pericardial tamponade due to a hydatid cyst has not yet been described in the literature. We present the case of a 46-year-old woman who presented to the Emergency Department with complaints of chest pain and mild dyspnea. Her medical history was positive for a liver hydatid cyst operation 26 years earlier. She was tachypneic, tachycardic, and hypotensive. Pleural and pericardial effusions were detected on transthoracic echocardiography. When she worsened clinically, pericardiocentesis was performed and she promptly improved. A fistula was detected between the liver and pericardium on computed tomography (CT) scan of the torso. Serologic test (agglutination) for Echinococcus granulosus was positive in a 1/32 dilution. A final diagnosis of mediastinal hydatic cyst was made, and a 4-week course of albendazol was given. Then the cyst was surgically excised, and the patient recovered without complications. (C) 2010 Elsevier Inc.