Background : Intravascular ultrasound (IVUS) has been known to be useful in percutaneous coronary intervention (PCI) for optimal stent deployment. However, in drug-eluting stent (DES) era, it is not well known whether IVUS during PCI has a significant impact on clinical and angiographic outcomes. So, this study was performed to evaluate the of IVUS use during PCI. Methods and results : Total 418 patients who underwent PCI with DES between April 2003 and January 2007, were classified into 2 groups of IVUS-guided PCI group(IVUS group) and IVUS-nonguided group(non-IVUS group). IVUS group included the patients that all DES implantations were guided by IVUS. Baseline clinical characteristics were not significantly different between 2 groups. At 6 months and 12 months clinical follow-up, there were no major differences in death, myocardial infarction, stent thrombosis, target lesion revascularization(TLR), target vessel revascularization(TVR), and major adverse cardiac events(MACE) (All p > 0.05). Also, in subgroup analysis, there were no significant differences. In turn, we enrolled 787 lesions of DES implantation, classified into 2 groups as previously. Baseline clinical characteristics were not significantly different between 2 groups. At 6 and 12 months follow-up, there were no significant differences. However, in lesions with diabetes, a trend was seen in favor of the non-IVUS group in TVR (at 6 months; 5.7% vs. 2.1%; p=0.066: at 12 months; 12% vs. 6.3%: p=0.056). In terms of angiographic characteristics, baseline reference vessel diameter (RVD) and minimal lumen diameter (MLD) were smaller in non-IVUS group than IVUS group (2.57mm vs. 2.77mm, 0.69mm vs. 0.78mm, respectively). However, percent diameter stenosis was not different. After PCI, acute gain was smaller in non-IVUS group (1.63mm vs. 1.75mm; p=0.039). At follow-up (median: 195days), late loss was smaller in non-IVUS group (0.36mm vs. 0.47mm; p=0.017). Conclusions : This study showed that routine use of IVUS might have no definite benefit on clinical and angiographic outcomes. Nonetheless, using IVUS, we could make more acute gain in PCI, even though late loss is larger. In diabetic patient, routine use of IVUS may give rise to TVR more frequently.