Objective To investigate and analyze the impact of gender difference on outcome and prognosis of ST-segment elevation myocardial infarction (STEMI) in patients treated with primary percutaneous coronary intervention (PCI).Methods This was a prospective and multicentered observation study.All the patients with acute STEMI admitted to the hospitals from June 1st 2009 to June 1st 2010 were continuously recruited.In this study,a unified questionnaire was applied and the 382 patients satisfied the criteria.A unified follow-up questionnaire was used on patients who were discharged from the hospital.Results On average,the female patients were 8 years older than the males.The median “symptom-to-balloon time” was 312.5 minutes in females and 270.0 minutes in males,and it was significantly different (P=0.007).During hospitalization,a higher proportion of female patients developed heart failure,angina and bleeding.No gender differences were found on the in-hospital mortality rates and medical therapy recommended by the guideline.The female patients were more prone to multi-vessel disease than males (P=0.002).Success rates of primary PCI did not show any gender differences.One-month mortality and other cardiovascular events also did not show gender difference when the patients were followed for one month after being discharged.The rates of heart failure and re-hospitalization due to cardiac incidents among female patients were obviously higher than the males,three months after being discharged (P=0.007,respectively).However,the three-month and long-term cardiac mortality did not show differences related to gender.Female patients were associated with higher all-cause mortality than that in males,but there was no statistically significant difference (female 4.2％ vs.male 1.6％;P=0.056).Data from multi-factor regression analysis showed that being female was not an independent predictor related to in-hospital mortality or during the follow-up period.Conclusion Being female was not an independent predictor of in-hospital mortality or during follow-up period among patients who were treated with primary PCI.Worse long-term outcome seen in female patients was likely to be explained by older age or longer pre-hospital delayed time.