Abstract： Background The optimal reperfusion strategy in elderly patients with ST-elevation myocardial infarction (STEMI) remains unclear. The purpose of this study was to evaluate the safety, in-hospital and one-year clinical outcomes for patients ＞75 years of age with STEMI receiving primary percutaneous coronary intervention (PCI),compared with those treated by conservative approach.Methods One hundred and two patients ＞75 years of age with STEMI presented ＜12 hours were randomly allocated to primary PCI (n=50) or conservative therapy only (n=52). The baseline characteristics, in-hospital outcome and major adverse cardiac events (MACE), including death, non-fatal myocardial infarction and target vessel revascularization at one-year clinical follow-up were compared between the two groups.Results Age, gender distribution, risk factors for coronary artery disease, infarct site and clinical functional status were similar between the two groups, but the patients in primary PCI group received less low-molecularweight heparin during hospitalization. Compared with conservative group, the patients in primary PCI group had significantly lower occurrence rate of re-infarction and death and shortened hospital stay. The composite endpoint for in-hospital survivals at 30-day follow-up was similar between the two groups, but one-year MACE rate was significantly lower in the primary PCI group (21.3% and 45.2%, P=0.029). Left ventricular ejection fraction was not significantly changed in both groups during follow-up. Multivariate analysis revealed that primary PCI (OR=0.34, 95% CI: 0.21-0.69, P =0.03) improved MACE-free survival rate for STEMI patients aged ＞ 75 years.Conclusion Our results indicated that primary PCI was safe and effective in reducing in-hospital mortality and one-year MACE rate for elderly patients with STEMI.