Objectives: The purpose of this study was to evaluate the use of distal protection during percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI) in native coronary vessels. Background: Embolization of material from the infarct-related lesion during PCI may result in impaired myocardial perfusion and worsen the prognosis. Previous attempts to protect the microcirculation during primary PCI have had conflicting results. Methods: We randomly assigned 626 patients with STEMI referred within 12 h to have PCI performed with (n = 312) or without (n = 314) distal protection. The primary end point was complete (≥70%) ST-segment resolution detected by continuous ST-segment monitoring. Blood levels of troponin-T and creatine kinase-MB were monitored before and after the procedure, and echocardiographic determination of the left ventricular wall motion index (WMI) was performed before discharge. Results: Patients were well matched in terms of demographic and angiographic baseline characteristics. There was no significant difference in the occurrence of the primary end point (76% vs. 72%, p = 0.29), no difference in maximum troponin-T (4.8 μg/l and 5.0 μg/l, p = 0.87) or maximum creatine kinase-MB (185 μg/l and 184 μg/l, p = 0.99), and no difference in median WMI (1.70 vs. 1.70, p = 0.35). The rate of major adverse cardiac and cerebral events (MACCE) 1 month after PCI was 5.4% with distal protection and 3.2% with conventional treatment (p = 0.17). Conclusions: The routine use of distal protection by a filterwire system during primary PCI does not seem to improve microvascular perfusion, limit infarct size, or reduce the occurrence of MACCE (Drug Elution and Distal Protection During Percutaneous Coronary Intervention in ST Elevation Myocardial Infarction; NCT00192868).