OBJECTIVE: To measure the serum levels of brain natriuretic peptide (BNP) in patients with chronic chagasic heart disease and in individuals with positive serology for Chagas’ disease and no heart impairment, and to correlate the serum BNP levels with the degree of cardiac impairment, cardiac dimensions, presence of a pacemaker, and ejection fraction. METHODS: Serum BNP concentrations were determined by use of the Triage – BNP Test produced by BIOSITE. Serum BNP was assessed in 25 patients from the Chagas’ disease outpatient clinic of the Hospital Universitário Oswaldo Cruz, who were divided into 2 groups as follows: 1) G1 – comprising 13 assymptomatic patients with positive serology for Chagas’ disease and no heart disease detectable on electrocardiography, chest X-ray, and echocardiography; and 2) G2 – comprising 12 patients with Chagas’ disease and heart impairment. RESULTS: Significantly more elevated BNP levels were detected in the chagasic patients with cardiac impairment: (G1=4.4 ±4.4 pg/ml, G2=293.0±460.2 pg/ml); (P<0.01). In the 2 groups, the serum levels of BNP correlated neither with age nor with sex. The levels were directly proportional to functional class and cardiac area on chest X-ray. Although a trend towards an increment in systolic function impairment was observed, no linear correlation with the ejection fraction on echocardiography occurred. The presence of definitive pacemaker and electrocardiographic alterations did not change the serum BNP levels. CONCLUSION: Asymptomatic individuals with a positive serology for Chagas' disease and no evidence of ventricular dysfunction have serum BNP levels similar to those of the general population.