The authors studied the files of 111 patients (mean age 47.5 years) with chronic Chagas' disease and severe heart failure who had died between 1978 and 1984; they were 72 men and 39 women. Eighty-one patients (73%) had cardiac thrombosis, 65 times (53%) in right chambers and 56 times (46%) in left ones. Sixty-seven patients (60%) had thromboembolic episodes, 41 (65%) to the lungs, 23 (38%) to other organs (target organs: the kidneys in 21 cases, spleen in four, brain in two, abdominal aorta in one, mesenteric artery in one and iliac artery in one). Right chamber thrombosis occurred 65 times, 35 (53%) with pulmonary thromboembolism. Left chamber thrombosis occurred 56 times, 24 (42%) with systemic thromboembolism. A total of 41 patients had pulmonary thromboembolism, only six (14%) without right chamber thrombosis; of 26 patients with systemic thromboembolism, only two (7%) did not have left chamber thrombosis. The authors concluded that the incidence of thrombosis and thromboembolism was high in the group studied, and that there was a relationship between chamber thrombosis and systemic or pulmonary thromboembolism.