With the purpose of analyzing diastolic function in Chagas, disease (ECh), 42 patients were studied: 31 males (aged 33 +/- 9), 22 of them with positive serology for ECh and 9 with negative serology; 11 female patients (aged 36 +/- 12), 10 with positive serology and 1 with negative serology. In all patients 2 D-Echo and simultaneous EKG, phonocardiogram, apexcardiogram and M-mode Echo at 100 mm/sec were taken. The A2-D, A2-O (total apexcardiographic relaxation-RAT), a/D (diastolic amplitude of "a" wave), ITRAT = A2 - C/RAT, DDVI, DSVI, shortening fraction (FA) and percentage of dimension changes (D D%) were determined. The patients were divided into 4 groups: G - A (n = 10) normal; G - B (n = 15) positive serology, with EKG and Rx and FA normal; G - C (n = 10) positive serology, abnormal EKG, and normal Rx and FA; G - D (n = 7) positive serology, abnormal EKG, mild cardiomegalia and diminished FA. The patients from group B presented significative modification, 46& (7/15) of the FD indexes and those from group D with 70% (5/7), as well as of D D C - E and D D Dm-0 indicative of uncoordinated contraction and relaxation. A progressive worsening of the FD from G - D was observed, reaching in this last one statistically significant values. In the ECh the alterations in the FD precede the systolic, which allows for an early detection of myocardiac damage by noninvasive techniques.