Background: Primary stenting for ST-segment elevation myocardial infarction(STEMI) has been shown to improve the outcome because of the benefits in terms of restenosis. However, still controversial are the benefits in terms of reperfusion. In the Zwolle-6 randomized trial, a consecutive cohort of patients with STEMI was randomized to balloon angioplasty or stenting, without exclusion criteria. In this study, we analyzed data on myocardial perfusion and the extent of myocardial necrosis. Methods: From April 1997 to October 2001, a total of 1683 consecutive patients with STEMI were randomized to stenting or balloon angioplasty. No exclusion criteria were applied. Myocardial perfusion was evaluated by myocardial blush grade and ST-segment resolution. The extent of myocardial necrosis was evaluated by enzymatic infarct size and predischarge ejection fraction. All data were prospectively collected. Results: A total of 785 patients(92.5%) in the stent group and 763 patients(91.5%) in balloon group underwent primary angioplasty. The 2 groups showed similar baseline characteristics. No difference was observed between stent and balloon in myocardial blush grade, complete ST-segment resolution, distal embolization, enzymatic infarct size, and predischarge ejection fraction at both intention-to-treat and actual treatment analysis, even when restricted to patients with anterior infarction. Time delay to treatment(earlier or later than 6 hours) did not affect the results. No difference was observed in 1-year mortality(6.0%vs 5.9%, P=NS). Conclusions: As compared with balloon angioplasty, routine stenting does not improve myocardial perfusion, the rate of distal embolization, and the extent of myocardial necrosis in a large cohort of unselected patients with STEMI. Background: Primary stenting for ST-segment elevation myocardial infarction (STEMI) has been shown to improve the outcome because of the benefits in terms of restenosis. However, still controversial are the benefits in terms of reperfusion. In the Zwolle-6 randomized trial, a consecutive cohort of patients with STEMI was randomized to balloon angioplasty or stenting, without exclusion criteria. In this study, we analyzed data on myocardial perfusion and the extent of myocardial necrosis. Methods: From April 1997 to October 2001, a total of 1683 consecutive Patients with STEMI were randomized to stenting or balloon angioplasty. No exclusion criteria were applied. Myocardial perfusion was evaluated by myocardial blush grade and ST-segment resolution. The extent of myocardial necrosis was evaluated by enzymatic infarct size and predischarge ejection fraction. All data were prospectively collected. Results: A total of 785 patients (92.5%) in the stent group and 763 patients (91.5%) in balloon No difference was observed between stent and balloon in myocardial blush grade, complete ST-segment resolution, distal embolization, enzymatic infarct size, and predischarge ejection fraction at both intention-to-treat and actual treatment analysis, even when restricted to patients with anterior infarction. Even delay to patients with anterior infarction. earlier or later than 6 hours did not affect the results. No difference was observed in 1-year mortality (6.0% vs 5.9%, P = NS). Conclusions: As compared with balloon angioplasty, routine stenting does not improve myocardial perfusion, the rate of distal embolization, and the extent of myocardial necrosis in a large cohort of unselected patients with STEMI.