AIMS: It is unclear whether primary aspiration can prevent distal embolisation and thereby improve myocardial perfusion in patients presenting with acute myocardial infarction (AMI) within 12 hours after onset. METHODS AND RESULTS: At 24 centres in Europe and India, 249 AMI patients were randomised to primary aspiration with the Export aspiration catheter (Medtronic Vascular, Santa Rosa, CA, U.S.A.) followed by stenting (N=120) or to conventional stenting without primary aspiration (N=129). There were no significant differences between the 2 groups in baseline characteristics or target lesion TIMI scores. Procedure time was 36.7 +/- 18.0 minutes for primary aspiration followed by stenting versus 34.5 +/- 21.5 minutes for conventional stenting (P=0.08). Debris was obtained by primary aspiration from 85.3% of the arteries. The use of a bailout technique was significantly lower for primary aspiration than for conventional stenting (5.8% vs. 14.7%, P=0.02). For the primary endpoint of the combined rate of myocardial blush grade 3 and/or ST-segment resolution >50% to assess myocardial perfusion, primary aspiration followed by stenting was superior to conventional stenting (85.0% vs. 71.9%, P=0.025). Immediately postprocedure, the rate of myocardial blush grade 3 was 35.8% for primary aspiration followed by stenting versus 25.4% for conventional stenting (P=0.094). At 60 minutes post procedure, the rate of ST-segment resolution >50% was 73.5% for primary aspiration followed by stenting versus 64.8% for conventional stenting (P=0.218). Primary aspiration was also associated with a significantly higher postprocedure corrected TIMI frame count than conventional stenting (20 +/- 14.9 vs. 22.8 +/- 14, P=0.02). At 30 days, there were no differences between the treatments in the rate of major adverse cardiac and cerebral events. CONCLUSIONS: Compared with conventional stenting, primary aspiration with the Export aspiration catheter followed by stenting improved myocardial reperfusion in AMI patients presenting with TIMI flow grade 0 to 1. Further study of primary aspiration involving larger numbers of patients is warranted to assess its effect on longer-term clinical outcome.