Hospital transfer is associated with delays in performance of primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction. Given the limited number of interventional centers in the United States, the transfer of patients is widely practiced. We compared the outcome of patients who were transferred for primary PCI and determined whether prolonged door-to-balloon times were associated with increased mortality. Patients who presented within 12 hours with ST-segment elevation myocardial infarction and underwent transfer for primary PCI were identified from the National Registry of Myocardial Infarction database (NRMI databases 2, 3, and 4, n = 7,133). The short-term outcome of those who received early (< or =2 hours) was compared with that of those who received delayed primary PCI (>2 hours) using multivariate logistic regression analyses and propensity score methods. The door-to-balloon time for the early PCI group compared with the delayed PCI group was 99 +/- 16 versus 264 +/- 178 minutes, respectively (p <0.0001). The early PCI group had less recurrent ischemia and angina (5.8% vs 10.1%, p <0.001), less cardiogenic shock (5.1% vs 8.9%, p <0.001), and shorter length of hospital stay (4.4 +/- 3.5 vs 5.4 +/- 4.7 days, p <0.001). In-hospital mortality was lower for the early PCI group than for the delayed PCI group (2.7% vs 6.2%, p < 0.001; entire cohort 5.7%). Comparison of patients matched on propensity score (n = 993) showed that mortality was lower in the early than in the delayed PCI group (2.6% vs 4.6%, p = 0.014, c-statistic 0.67). In conclusion, <4% of patients who received PCI were treated within the recommended guideline of < 120 minutes by the American College of Cardiology/American Heart Association. Door-to-balloon times <2 hours in patients who undergo transfer for PCI is associated with a significant decrease in short-term mortality, which suggests that efforts must be made to decrease transfer delays.