Objective:To assess the safety and efficacy of simultaneous intravenous plus intracoronary administration of tirofiban bolus for patients with acute ST-elevation myocardial infarction(STEMI) undergoing primary percutaneous coronary intervention (PCI).Methods: Forty-three patients with acute STEMI ready to receive primary PCI were randomly divided into tirofiban IV group (intravenous tirofiban bolus only before stent deployment,n=22) or tirofiban IV&IC group (intravenous plus intracoronary administration of tirofiban bolus simultaneously,n=21).The thrombolysis in myocardial infarction trial and perfusion of the myocardium were observed before and after PCI.Major adverse cardiovascular event (MACE),hemorrhage event,and thrombocytopenia were observed during hospital stay; MACE was also observed 30 days after PCI.Results: The clinical characteristics and baseline angiographic findings were similar in the two groups.After PCI,no difference was observed in the final TIMI flow grade 3,CTFC≤27,sumSTR≥70% between the two groups (P=0.951,0.933,0.666,respectively).There was no significant difference in the frequencies of MACE (P=0.101) and the left ventricular ejection fraction between the two groups (P=0.694).No major hemorrhage or severe thrombocytopenia were found in the two groups during hospital stay.The total rate of bleeding was also similar in the two groups (P=0.558).The frequencies of MACE were similar in the two groups 30 days after operation.Conclusion: Simultaneous intravenous and intracoronary administration of tirofiban bolus is safe for STEMI patients undergoing primary PCI; the short-term efficacy is similar to that of intravenous administration only. PCI，and the short-term efficacy is similar to intravenouse administration only.