The role of heart transplants for treating Chagas' heart disease is not quite clear. Immunosuppression could lead to resurgence of T. cruzi infection with acute or chronic damage to the allograft. There are few publications regarding this issue. Thus we reported the follow-up of 18 patients with Chagas' heart disease submitted to orthotopic heart transplants from 1985 to 1993 at The Heart Institute. The patients were in functional class IV or Ill, or II, with sustained ventricular tachycardia episodes. The mean left ventricular ejection fraction was 25 +/- 9 percent and the mean right ventricular ejection was 22 +/- 6 percent (MUGA). lmmunosuppression was based on cyclosporin, azathioprine and corticosteroids. For specific post-transplant monitoring of T. cruzi infection, blood tests were performed (examination of blood or leukocyte concentrate, Giemsa-stained blood smears, blood culture, xenodiagnosis, mouse inoculation) and tissue biopsy (skin or myocardium). In addition, complement fixation hemagglutination and immunofluorescence assays were performed. T. cruzi parasitemias were detected in 18 circumstances in 13 patients. Resurgence of Chagas' disease was diagnosed in 11 circumstances in 5 patients. Fever, subcutaneous nodules and myocarditis predominated in these episodes. All episodes of parasitemia and Chagas' disease resurgence were successfully treated with benzonidazole. All surviving patients had normal cardiac function despite left ventricular function worsening during some myocarditis episodes. Neoplasias were important findings and 3 patients developed lymphoproliferative disease, 2 developed Karposi's sarcoma and 1 patient developed skin cancer. The survival rates at 4 and 12 months were 83 percent and 49 percent respectively. The survival of patients who underwent heart transplants from August 1991 to April 1993 was 100 percent at 4 months and 75 percent at 12 months. Heart transplants for Chagas' heart disease may be associated with episodes of parasitemia and a reoccurrence of episodes of Chagas' disease. The survival of heart transplanted patients has improved when associated with lower doses of cyclosporins and thus, fewer resurgences of the disease.