Abstract Background: In ST-elevation myocardial infarction (STE-MI), the association between either the grade or location of coronary thrombi with major adverse cardiovascular events (MACE) is controversial. Aim of Study: We created a novel index “thrombus score" through multiplying the TIMI thrombus grade by a segment weighing factor adopted from Gensini score. We hypothesized this thrombus score can better reflect the prognostic relevance of coronary thrombi. Patients and Methods: We prospectively studied 364 consecutive patients with anterior STEMI treated by primary percutaneous coronary intervention (PCI). Patients were followed-up for major adverse cardiovascular events (MACE) defined as the composite of repeated myocardial infarction, target vessel revascularization, stent thrombosis, stroke; and all-cause mortality. Results: 47 (12.9%) patients developed MACE. In the MACE group, percentage of female patients (p=0.004), base-line and peak HsTnT (<0.001; each), thrombus score (p < 0.001) were significantly higher. Conversely, LVEF at discharge was significantly lower in the MACE group (p=0.02). Using Cox regression analysis, only thrombus score (p < 0.001) and LVEF (p=0.01) were found as independent predictors of MACE. By ROC curve analysis, thrombus score at a cutoff value of >!7.5 was associated with MACE at 1 year with a sensitivity of 85% and specificity of 90% (AUC: 0.87, 95% CI: 0.83-0.93, p < 0.001). Conclusion: In STEMI patients treated with primary PCI, the novel angiographic “thrombus score" was the strongest independent predictor of MACE during the first year. Further studies are recommended to better understand and validate this novel score.