Chagas' disease can reactivate in patients with AIDS and present as a brain mass lesion or an acute diffuse meningoencephalitis indistinguishable from other opportunistic infections or neoplastic processes, such as toxoplasma encephalitis or central nervous system (CNS) primary lymphoma. The CNS tumor-like lesion is the most common manifestation of Chagas' disease reactivation in AIDS patients. The prognosis of untreated cases is grim and underscore the need for safe and effective therapeutic agents.