A 46-year-old female patient with chronic Chagas' myocarditis without heart failure was submitted to chemotherapy because of Hodgkin's disease. During treatment the frequency of polymorphic ventricular extrasystoles raised and the patient died by a sudden cardiac arrest. Autopsy revealed chronic Chagas myocarditis with an acute exacerbation. Nests of amastygotes with a density of up to 14 pseudocysts/cm2 were found in the myocardium, although restricted to the septum and left ventricular posterolateral wall. Extensive histologic examination did not reveal parasites in other locations. This favors the concept of a localized exacerbation of Chagas' disease due to immunosuppression developing from a persistent parasitic focus in the heart. Although this reactivation during chemotherapy of malignant disease is rarely reported in literature, a careful monitoring of patients with positive Chagas' serology during chemotherapy is recommended.