Two patients with cardiac tamponade, later found to be due to amebic pericarditis, presented in the space of two months. Both patients survived the initial tamponade and were treated for amebiasis. The first patient progressed to a complete clinical cure but the second patient died, probably as a result of the development of constrictive pericarditis. Diagnosis was made in both patients on the basis of an abscess in the left lobe of the liver (confirmed by liver scan and surgery), the presence of brown, sterile pus in both the liver abscess and pericardium, and high titers of amebic hemagglutinating antibodies in the blood. One of the patients is a native American who had not left Chicago for 30 years. She is thought to represent the first case of amebic pericarditis arising in the United States.