Abstract： Objective Atherosclerosis is widely accepted as a chronic inflammatory disease. Serum biomarkers for vulnerable plaques not only serve as diagnostic tools for the identification of patients with acute coro-nary syndrome, but also assist the identification of high-risk patients. However, the existing data are limited and conflicting. In the present study, we determined whether the plasma levels of interleukin-1β (IL-1β) are correlated with adverse cardiac outcomes in patients with ST-evaluate acute myocardial infarction (STEAMI) undergoing pri-mary percutaneous coronary intervention (PCI). Effect of the plasma intedeukin-1β level on prognosis of patients with ST-segment elevation acute myocardial infarction. Method This prospective single-center study included 96 patients with SIEAMI with onset < 12 h who underwent primary PCI, 271 patients with stable angina pectoris (SAP) and 148 control subjects without coronary artery disease who were consecutively admitted to hospital be-tween Mar, 2006 and Mar, 2008. Plasma IL-1β levels were measured by enzyme-linked immunosorbent assay in all subjects. The patients with STEAMI were then followed prospectively for the occurrence of major adverse car-diac events (MACE) (including cardiovascular death, non-fatal myocardial infarction, heart failure, and cardio-genie shock) during hospitalization. We determined the association between IL-1β levels with the risk of MACE using multivariate logistic regression. Results Compared with the SAP patients and control subjects, patients with STEAMI had higher levels of IL-1β (P < 0.05). During hospitalization, 32 patients (33.3%) experienced MACE [23 males, 9 females; age: (75.44±13.45) years]. In the STEAMI patients, IL-1β was elevated in patients with MACE compared with patients without MACE (median [range]: 26.52 [12.010 to 155.244] pg/mL vs 2.157 [0.433 to 83.021] pg/mL; P < 0.01) by non-parameter analysis. Significant and positive correlations be-tween IL-1β and cardiac troponin-I (cTnI) (r = 0.353, P =0.004) were observed by Spearman's correlations analysis. Multivariate logistic regression analysis revealed that IL-1β levels ≥20 pg/mL were significantly and in-dependently associated with MACE during hospitalization (odds ratio: 32.05; 95% confidence interval: 4.28 to 240.151; P =0.001). Conclusions The present study revealed that patients with STEAMI had elevated IL-1β levels on admission. The plasma IL- 1β level is an independent inflammatory predictor for in-hospital MACE in pa-tients with STEAMI undergoing percutaneous coronary intervention.