Objective: This study evaluated the effect of early application of intra-aortic balloon pump (IABP) counterpulsation in patients with ST-segment elevation acute myocardial infarction (STEMI), scheduled for elective percutaneous coronary intervention (PCI). Methods: Patients who had experienced STEMI for 12-72 h received (IABP group) or did not receive (control group) IABP counterpulsation for 3-5 days before PCI. Results: One hundred patients were included. Frequencies of infarct-related artery thrombolysis in acute myocardial infarction (TIMI) flow rate classes 0, I and II in the IABP group (11.5, 1.9 and 7.7%, respectively) were significantly lower than in the control group (29.1, 14.6 and 22.9%, respectively) before PCI. After PCI, the frequency of TIMI class III flow rate in the IABP group (96.2%) was significantly higher than that in the control group (81.3%). Four weeks after PCI, the left ventricular ejection fraction (LVEF) was significantly higher, and the incidence of major cardiac events was significantly lower, in the IABP group compared with the control group. Conclusions: Early use of IABP counterpulsation in STEMI patients scheduled for PCI was effective, with a favourable safety profile. IABP counterpulsation reduced the incidence of major adverse cardiac events and improved LVEF. However, IABP devices must be used at an early stage, to obtain optimal results.