Âbstraet-Vàz present paper deals with the analysis of the High Resolution Surface Electrocardiogram in patients with Chagas disease. The spectral estimation technique is based on the Discrete Fourier Transfom (DFT). evaluated over a 300 milliseconds segment situated around the QRS wave in the averaged signal, corresponding to three orthogonal derivations X, Y and Z. The results are presented as a spectro-temporal mapping of the signal and a comparison between normal subjects and patients with Chagas' disease based on the area between 0 and 300 Hz for a 76 milliseconds frame including the end of the QRS.