Abstract: AIM To explore the correlation between residual platelet agglutination (RPA) and plasma chemokine CCL2 concentration in patients with ST elevated myocardial infarction (STEMI) 4-6 h after taking clopidogrel. METHODS We enrolled 107 STEMI patients and each patient took clopidogrel (600 mg) and aspirin (300 mg) orally. Approximately 6 ml of venous blood was drawn 4-6 h after taking clopidogrel. We tested RPA using TPA and detected plasma CCL2 concentration using ELISA. Patients were divided into two groups: high platelet reactivity group and normal platelet reactivity group. The cutoff value was 59%. General data and clinical trial data were collected. RESULTS Fifty-one patients were in the high platelet reactivity group and 56 patients were in the normal platelet reactivity group. Age, gender, smoking history, hypertension history, diabetes mellitus history, FG, TC, TG, HDL-C, LDL-C and BNP were not significantly different between groups. There was a linear correlation between RPA and plasma CCL2 concentration in the 107 STEMI patients (r=0.427, P<0.01). Plasma CCL2 concentration was significantly different between groups (P<0.01). Plasma CCL2 concentration was, respectively (243±80) ng/L in high platelet reactivity group and (171±44) ng/L in normal platelet reactivity group. TNT and CK-MB levels in high platelet reactivity group were, respectively, higher than those in the normal platelet reactivity group ［(3.1±2.3) U/L vs.(2.3±1.4) U/L; (198±16) μg/L vs.(151±13) μg/L; both P<0.05］. CONCLUSION A linear correlation exists between RPA and plasma CCL2 concentration.