Chagas disease, caused by a hemoflagellate,Trypanosoma cruzi, is a parasitic disease widelydistributed throughout Latin America. It is trans-mitted to man by hematophagous vectors (redu-viid bugs), blood transfusion and, more rarely, byoral route, laboratory accidents, and from motherto fetus. About 18 million people are chronicallyinfected by this parasite in the Americas. The ma-jority of these individuals do not display signs orsymptoms of the disease (indeterminate phase), butas time goes by around 30% of the infected indi-viduals develop signs of cardiopathy and/or megae-sophagus/magacolon (MS Ferreira et al. 1997a ClinInfect Dis 25: 1397-1400).From several decades, cases of reactivation ofChagas disease in immunocompromised individu-als have been recognized. The literature registerscases of T. cruzi meningoencephalitis and/or myo-carditis occurring in patients with hematologic can-cers (leukemias and lymphomas), kidney, bonemarrow and heart transplantation, and in individu-als using high doses of corticosteroids and otherimmunosupressors. The epidemic of acquired im-munodeficiency syndrome (Aids) opened the pos-sibility of the appearance of this parasitosis in in-dividuals seriously immunocompromised by thehuman immunodeficiency virus (HIV) andcoinfected with T. cruzi. In Brazil, nowadays, themajority of carriers of this infection live in big cit-ies, where cases of Aids are commoner; thereforeit is expected the occurrence of a growing numberof these reactivations in coinfected individuals. Inchagasic patients with hematologic cancers whoreactivate the infection it was observed the devel-opment of severe cases of meningoencephalitis andmyocarditis; the parasite, in general, can be easilyseen by direct examination of a blood smear. Themortality in these cases has been high, particularlyin those whose diagnosis is delayed. Treatment withnifurtimox or benznidazole can lead to remissionand decrease mortality substantially (MS Ferreiraet al. 1997b p. 365-379. In JC Pinto Dias & JRCoura, Clinica e Terapeutica da Doenca deChagas. Uma Abordagem Pratica para o ClinicoGeral, Fiocruz, Rio de Janeiro).The reactivation of chagasic infection also oc-curs in patients submitted to kidney or heart trans-plant who are treated with immunosupressivetherapy. T. cruzi infection can also be acquired, inthese cases, by the organ transplanted from achagasic donor. In patients submitted to kidneytransplant the clinical manifestations can be indis-tinguishable from the acute phase, with occasionalinvolvement of the central nervous system. Car-diac transplants carried out in patients with chronicchagasic cardiopathy have been uncommon, butreactivation of the trypanosomiasis occurs in themajority of the individuals, with clinical manifes-tations characterized by fever, signs of acute myo-carditis, characterized by cardiac failure or atrio-ventricular block, and erithematous-infiltrativecutaneous lesions whose histopathological studyreveals the presence of paniculitis with a largenumber of nests of T. cruzi within macrophages(Ferreira et al. 1997b loc. cit.).In patients with kidney transplant with reacti-vated Chagas disease, the finding of the parasite inthe blood smear is key to the diagnosis, but thisfinding is rare in patients with cardiac transplants.Therapy with benznidazole with usual doses (5 mg/kg/day for 60 days) suppresses efficiently the clini-cal symptoms, but obviously does not cure the para-sitosis. Another drug, allopurinol (600mg/day)seems to be safe and effective in the treatment ofChagas disease reactivation after heart transplan-tation (DR Almeida et al. 1996 Ann Thorac Surg61: 1727-1733). Secondary episodes of reactiva-tion can occur. It is important to note that Ameri-can trypanosomiasis is not a contraindication toany form of transplant, given that specific therapyis able, as already mentioned, to rapidly suppressthe clinical manifestations of reactivation (Ferreiraet al. 1997b loc. cit.).About 60 cases of Chagas disease reactivationin patients with Aids have been documented as ofDecember 1998, the majority of them only reportedin congresses and symposiums of the speciality; 19cases are published and the details of them can befound in two recent publications, where the subjectis discussed (Ferreira et al. 1997a loc. cit., AMCSartori et al. 1998 Clin Infect Dis 26: 177-179).