A 52yrs male presented with chest pain for 2hrs after exercise. He was current smoker, 15PYRs Admission via ER, EKG was revealed NSR(HR: 60BPM) with QS pattern on V1-V3 leads, as well as hyperacute T waves on V2-V3. Blood chemistry showed slightly elevated troponin-I (0.08 ng/ml). So, with the diagnosis of early phase of AMI, emergent CAG was performed, which revealed total occlusion of mid-portion of LAD. So, after engagement of guide catheter, Run-through guidewire was advanced to distal portion of LAD. Then, predilation with Ottimo 2.0×15 mm balloon catheter was performed at 14 atm for 15 seconds. After that, sluggish distal flow was obtained. So, IV injection and infusion of abciximab was initiated. Then, Taxus 3.5×38 mm was deployed and inflated at 10 atm for 10 seconds. After that, TIMI III distal flow was obtained but mid portion of stent was not fully expanded. So, adjuvant balloon inflation with same stent balloon was performed at 16 atm for 6 seconds. Then, abruptly distal flow was deteriorated and patient`s systolic blood pressure went down to 70 mmHg with complaint of severe chest pain. So, intracoronary adenosine was injected several times and thrombosuction with Thrombuster II was performed. Finally, TIMI II flow was obtained and patient was stabilized. Two days later after initial PCI, f/u CAG was performed, which revealed TIMI III distal flow of LAD. On IVUS examination, stent struts were well apposed to the vessel wall with mixed echogenic shadows behind the struts, suggestive of either residual thrombus or plaque, were observed at proximal third of stent. The patient was discharged after 1 week without angina and had been doing well during 6 months f/u period on dual antiplatelet therapy. After 6 month, the patient was readmissioned for follow-up CAG. On follow-up CAG, there was huge coronary aneurysm (max. diameter=7 mm, length=18 mm) on proximal portion of previous stent atmid-LAD. On IVUS examination, there were echo-free space behind the stent struts (suggesting aneurysm) toward multiple direction at proximal third portion of previous stent. However, the patient didn`t complained of any symptoms, so he was discharged with triple antiplatelet agents (aspirin+clopidogrel+cilostazol).