Abstract： Background ST-segment elevation myocardial infarction (STEMI) in elderly patients presents specific clinical characteristics.The study on percutaneous coronary intervention (PCI) in elderly patients (≥75 years) with STEMI,however, has less been performed.Methods In the present study, 522 consecutive STEMI patients undergoing PCI within 12 hours from symptom onset were investigated, and clinical characteristics and in-hospital and 6-month outcomes of 66 elderly patients (≥75 years,group A) were compared to those of 456 younger patients (＜75 years, group B).Results Compared to younger patients, elderly ones had more females (42.4% vs.17.8%, P ＜0.005), a history of cerebral vascular events (7.6% vs.0.9%, P ＜0.05), higher serum creatinine level ((96.48±31.65) mmol/L vs.(84.87±19.81)mmol/L, P＜0.005) and fewer smokers (28.8% vs.45.4%, P＜0.05).The elderly ones had worse Killip class (Killip I class:69.7% vs.85.7%, P ＜0.05), less drug-eluting stent implantation and lower rates of TIMI flow 3 following PCI (33.3% vs.47.1%, and 84.8% vs.94.7%, P ＜0.05 respectively).Additionally, both in-hospital mortality and myocardial infarction rate were found to be higher in elderly patients (16.7% vs.1.5%, and 7.6% vs.2.6%, P ＜0.05 respectively), which were also observed until 6-month follow-up (9.1% vs.0, and 6.1% vs.0, P ＜0.05 respectively＝.In multivariable Cox regression analysis, serum creatinine level, history of hypertension, left anterior descending coronary artery as infarct-related artery and Killip class were independent predictors of 6-month overall death in elderly patients.Conclusions The clinical characteristics of elderly patients with STEMI after PCI are different from those of younger patients.Although PCI in this population is with a low rate of PCI failure, it is still associated with a worse outcome.