Resolution of ST-segment elevation 180 min after thrombolysis for acute MI predicts acute outcomes, but if a 90-min ECG is also predictive earlier intervention is possible. This substudy enrolled 1783 pts from an international trial of alteplase vs. reteplase treatment within 6 h of MI. ECGs were obtained at baseline, 90, and 180 min after lytics. The sum of the ST-segment resolution at 90 and 180 min was categorized as <30%, 30%-70%, or >70% resolved versus baseline We compared groups to determine if ST resolution at 90 min was as predictive as at 180 min.Conclusion: Persistent ST-segment elevation as early as 90 min after thrombolysis is prognostically important, as is elevation persisting at 3 hours. These data should help identify pts who may benefit from early intervention. Treatment strategies should be developed for pts with continued ST-segment elevation after thrombolysis.