Three new cases of reactivation of Chagas' disease in patients with AIDS, with central nervous system and/or cardiac involvement, are reported. One patient had histological evidence of acute esophageal and gastric Trypanosoma cruzi myositis, a previously unrecognized finding in patients with reactivated Chagas' disease. The patients had a low CD4 lymphocyte count and had other AIDS-defining opportunistic infections. One patient's condition improved with benznidazole therapy. Analysis of these three cases and review of the 13 others published in the literature revealed that the central nervous system is the most commonly involved site (75%), followed by the heart (44%). Early diagnosis and treatment with benznidazole or nifurtimox probably improve the survival rate. Long-term secondary prophylaxis should be recommended for patients who respond to therapy, although it is uncertain which drug to use for this purpose. T. cruzi should be included in the list of opportunistic pathogens causing infection in severely immunocompromised patients with AIDS.