The purpose of this study was to determine if quantitative measurements of regional asynergy add independent prognostic information to global ejection fraction in patients with chronic coronary artery disease. Four hundred eighty-six patients with a history of Q-wave myocardial infarction who underwent gated-equilibrium radionuclide angiography at least 3 months after infarction were monitored for a median duration of 4.7 years. During follow-up there were 95 deaths. Four of five regional asynergy indexes analyzed were associated with overall mortality. The strength of the association between overall mortality and the index that proved to be optimal (univariate χ ² = 26.4, p < 0.001) was stronger than for global ejection fraction (univariate χ ² = 21.5, p < 0.001). For patients with global ejection fraction <40%, 4-year survival was 87% for those with a low asynergy index versus 65% for those with a high asynergy index (p = 0.016). In conclusion, indexes of regional asynergy add independent prognostic information to global left ventricular ejection fraction. (Am Heart J 1997;133:640-7).