Background: In acute myocardial infarction, increased neutrophil count has been associated with adverse clinical outcome. The association of neutrophil count with the myocardial injury of ST-segment elevation myocardial infarction (STEMI) is now being examined. Thrombus aspiration during primary percutaneous coronary intervention (PCI) can reduce the myocardial injury due to microvascular embolic obstruction for STEMI. The aim of this study was to assess whether the aspiration thrombectomy improve the myocardial injury even in the patient with high neutrophil count on admission. Methods: Aspiration thrombectomy was performed in patients with TIMI flow grade 0 or 1 and angiographically visible thrombus during primary PCI. 52 consecutive patients who underwent aspiration thrombectomy were evaluated. Neutrophil counts were measured before PCI. TIMI flow grade and TIMI myocardial perfusion (TMP) grade after revascularization were evaluated during PCI. Patients were categorized in 3 groups based on initial neutrophil counts: low(<7,000/���), intermediate (7,000-11.000/���), and high (>11,000/���). End point was the myocardial perfusion assessment using TMP grade after primary PCI. Results: All patients reached protprocedural TIMI flow grade 2-3, and 31 patients (60%) had TMP grade 3. Baseline TIMI flow grades were similar between groups of neutrophil. Patients in higher neutrophil group had a tendency of worse postprocedural TIMI flow (p=0.13) and negatively correlated with final TMP (p=0.02). Conclusion: Elevated neutrophil counts in patients with STEMI are directly related to myocardial injury even after thrombus aspiration during primary PCI. Further strategy to improve myocardial perfusion might be needed in this high risk subset of AMI patients.