The mortality benefit of thrombolytic therapy for acute myocardial infarction (AMI) is strongly dependent on time to treatment. Recent observations suggest that time to treatment may be less important with primary percutaneous transluminal coronary angioplasty (PTCA). Patients with AMI of <12 hours duration, without cardiogenic shock, who were treated with primary PTCA from the Stent PAMI Trial (n = 1,232) were evaluated to assess the effect of time to reperfusion on outcomes. Thrombolysis In Myocardial Infarction grade 3 flow was achieved in a high proportion of patients regardless of time to treatment. Improvement in ejection fraction from baseline to 6 months was substantial with reperfusion at <2 hours but was modest and relatively independent of time to reperfusion after 2 hours (<2 hours, 12.3% vs > or =2 hours, 4.2%, p = 0.004). There were no differences in 1- or 6-month mortality by time to reperfusion (6-month mortality: <2 hours [5.5%], 2 to <4 hours [4.6%], 4 to <6 hours [4.5%], >6 hours [4.2%], p = 0.97). There were also no differences in other clinical outcomes by time to reperfusion, except that reinfarction and infarct artery reocclusion at 6 months were more frequent with later reperfusion. The lack of correlation between time to treatment and mortality in patients without cardiogenic shock suggests that the survival benefit of primary PTCA may be related principally to factors other than myocardial salvage. These data may also have implications regarding the triage of patients with AMI for primary PTCA.