Objective To observe the effect of ischemia postconditioning during the first minutes of reperfusion for the myocardial reperfusion injury in ST-segment elevation acute myocardial infarction (STEMI)patients undergoing emergency percutaneeus coronary intervention(PCI). Methods STEMI patients undergoing emergency PCI in affiliated hospital of Beihua University between October 2006 and January 2009 were randomly divided into two groups: the control group(n = 34)without any intervention after PTCA, and the postconditioning group(n = 30)with ischemia postconditioning within first minutes of reflow by 3 episodes of 30-second inflation and 30-second deflation with the angioplasty balloon. Reperfusion arrhythmias, CK and CKMB, corrected TIMI frame count(CTFC), wall motion score index(WMSI)and left ventricular ejection fraction(LVEF)by echocardiography were compared between the two groups. MI areas were evaluated with the ECG-54 criteria/32 system and myocardial blush grade(MBG)was measured. Results The incidence of reperfusion arrhythmias-frequent ventricular premature(26. 7% vs.52. 9%)and short array ventricular tachycardia beat(23.3% vs. 58. 8%)as well as values of peaks CK [(l162±548)U/L vs.(1732±480)U/L, P＜0. 01], CKMB[(165±70)U/L vs.(280±99)U/L,P＜0. 01],CTFC(22.23 ±3.81 vs. 26.97 ±3.42), WMSI(1.27 ±0.52 vs. 1.82 ±0.83),and infarction areas determined by ECG methods(10. 60% ±4. 97% vs. 14. 65% ±6. 88%, all P ＜0. 05)were all significantly lower in the postconditioning group than in control group while LVEF(0. 55 ± 0. 08 vs.0. 47 ±0. 10)and MBG(2. 27 ± 0. 64 vs. 1.47 ± 0. 61, all P ＜ 0. 05)were signiticantly higher in the postconditioning group than in control group. Conclusions Ischemia postconditioning can significantly reduce myocardial reperfusion injury in patients with STEMI.