Cerebrospinal fluid (CSF) samples of 200 patients who presented central nervous system (CNS) pathologies were evaluated for antibodies to Trypanosoma cruzi (T. cruzi). The evaluation was made through: complement fixation test (CFT) in 69 patients, undirect (IgG) immunofluorescence test (IFT) in 118, and by CFT and IFT in 13. In 50 cases the IFT has been made also in concentrated (20 X) CSF samples. Results were evaluated in report to CNS pathology, CSF cells and proteins, and tests in the CSF for other CNS infections (syphilis, cysticercosis, schistosomiasis, toxoplasmosis). These tests were based on techniques similar to those adopted for the search of antibodies to T. cruzi, and were conducted concomitantly to tests for T. cruzi in the same CSF sample for everyone of the cases. Antibodies to T. cruzi were found in three patients. The first was a patient committed by the acquired immunodeficiency syndrome (AIDS) in whom there occurred exacerbation of the acute stage of Chagas' disease. The second is a patient who is committed by epilepsy, and an acute stroke occurred in the third patient; Chagas' disease had been previously diagnosed in them through the demonstration of antibodies to T. cruzi in the blood serum.