Abstract: AIM:To investigate the efficacy of early application of low-dose tirofiban in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). METHODS: A total of 77 STEMI patients were randomly divided into tirofiban group (n=39) and control group (n=38). PCI was performed in all patients within 12 h after onset of STEMI and patients were given an oral bolus dose of clopidogrel 300 mg and aspirin 300 mg before PCI. Tirofiban 2/3 (10 μg/kg bolus) was injected into the artery (IRA) during PCI and intravenously administered for 24h ［0.1μg/(kg·min)］ after PCI in tirofiban group. The thrombolysis in myocardial infarction (TIMI) flow grade, ST-segment complete recovery rate within 24 h, left ventricular ejection (LVEF), major adverse cardiac events (MACEs, including death, re-infarction, target vessel revascularization, recurrent angina pectoris) and TIMI bleeding events were recorded. RESULTS: Baseline data (including age, gender, risk factors and duration of hospitalization) of the two groups were comparable. Immediate TIMI flow grade after PCI in low-dose tirofiban group was significantly higher than in control group (all P<0.05). ST-segment complete recovery rate within 24 h and LVEF at 1 week in low-dose tirofiban group were also significantly higher than in control group (P<0.05, P<0.01). MACE rate in the two groups at 1 month was similar (P>0.05) and the incidence of major bleeding in the two groups was also similar. CONCLUSION: Intracoronary application of low-dose tirofiban during primary PCI is safe and effective for improving TIMI flow of IRA in patients with STEMI during primary PCI.