Backgrounds: Whether the additional ballooning using stent balloon or another commercially available balloon after drug-eluting stent (DES) implantation at routine percutaneous coronary intervention (PCI) is beneficial in terms of clinical and angiographic parameters is not clarified yet. We sought the efficacy of additional balloon strategy after DES implantation up to 6 months. Methods: The study population consisted of 343 patients (pts, male 234, mean age 62.2 짹10.4 years) who underwent standard PCI with DES, either Sirolimus-eluting stent (SES; Cypher) or Paclitaxel-eluting stent (PES; Taxus). Clinical and angiographic parameters of 276 pts with additional balloon group were compared with those of 67 pts without additional balloon group. Results: Baseline clinical and procedural characteristics were similar between the two groups. Mean balloon pressure in additional balloon group was 9.7 짹 3.5 atm. At 6 months, binary restenosis was significantly lower in the additional balloon group (1.5% vs. 5.8% in no additional balloon group, p=0.04). Mean % restenosis was similar between two groups (31.0 % vs. 30.1 % in no additional balloon group, p=NS). Major adverse cardiac event (MACE) was significantly lower in the additional balloon group (1.5 % vs. 7.6% in no additional balloon group, p=0.02, Table). Conclusion: Additional ballooning after DES implantation showed excellent angiographic and clinical outcomes including lower binary restenosis and MACE compared to those of the pts without additional ballooning. Routine additional ballooning just after DES implantation should be encouraged for better angiographic and clinical outcomes in contemporary PCI.