Extraction and measurement of biogenic amines (norepinephrine, dopamine, serotonin and histamine) were carried out on human ventricular myocardium obtained from autopsies of individuals divided in the three following groups: chronic Chagas' heart disease (with congestive heart failure: 16 cases, and with sudden and unexpected death: 13 cases); hypertensive heart disease (12 cases); and control patients (with no heart disease: 12 cases). The myocardial samples were obtained from the free walls of left and right ventricles and from the apex. A significant depletion of norepinephrine was detected in those with congestive failure. A poorly elevated level of dopamine was also seen in right ventricular and apical myocardium from those with failure. Left ventricular and apical concentration of serotonin were significantly elevated in the presence of hypertensive heart disease. The most important findings were obtained with histamine, which is increased in both groups of Chagasic patients. We believe that the approach here reported may provide useful informations on the pathogenetic mechanisms, thus far poorly understood, of chronic Chagas' heart disease.