Thrombolytic therapy clearly reduces mortality in patients with acute myocardial infarction, especially when initiated within 6 hours of onset of symptoms. Some studies have also suggested that thrombolytic therapy may improve survival even when initiated 6-24 hours after the onset of symptoms by mechanisms other than infarct size limitation, such as reduced expansion, reduced electrical instability, and improved healing of the infarct. However, in view of the possibility that late thrombolytic therapy may also be associated with an increased risk of cardiac rupture, the risk-benefit ratio needs to be more clearly defined. Ongoing randomized trials are expected to clarify the situation in the near future. In the meantime, efforts to initiate reperfusion as soon after the onset of myocardial infarction as possible should continue, since early treatment is still the best treatment.