The T-wave axis shift has been reported to represent a general marker of ventricular repolarization abnormalities and a potential indicator of increased risk for cardiovascular mortality. We assessed the prognostic importance of the T-wave axis deviation for mortality rate in patients with chronic Chagas' disease. In a long-term follow-up prospective study, 738 adult outpatients in the chronic phase of Chagas' disease were enrolled. The frontal plane T-wave axis was estimated from 12-lead electrocardiograms obtained on admission and categorized as normal (15° to 75°), borderline (75° to 105° or 15° to −15°), and abnormal (>105° or < −15°). Clinical and radiologic data, 2-dimensional echocardiographic data, and other electrocardiographic data were also recorded. Primary end points were all-cause, those related to Chagas' disease, and sudden cardiac deaths. Statistical analyses included Kaplan-Meier estimation of survival curves and multivariate Cox's proportional hazards models. During a follow-up of 58 ± 39 months, 62 patients died, 54 from causes related to Chagas' disease and 40 due to sudden cardiac death. Kaplan-Meier survival curves showed that the 3 categories of T axis had significantly different prognoses. Multivariate Cox's survival analysis demonstrated that an abnormal T axis increases the risk of death threefold and sudden death nearly sixfold after adjustment for other covariates, including left ventricular systolic function and other electrocardiographic abnormalities. Borderline T-wave axis also indicated a worse prognosis, particularly in the subgroup of patients with abnormal baseline electrocardiograms. These results indicate that T-wave axis deviation is an easily quantified, strong, and independent mortality risk predictor in patients with chronic Chagas' disease.