Background and Objectives: During percutaneous coronary intervention for bifurcation lesion with drug eluting stent (DES), guidewire may be used to protect side branch (SB). After deploying DES at main vessel, withdrawal of SB guidewire may damage the polymer of DES strut or vascular wall, which may enhance the risk of late loss in main vessel or os of SB. The aim of this study was to evaluate 6 months��� angiographic outcome of main vessel DES stenting with jailed SB wire versus DES stenting without SB wire and major adverse cardiac events(MACE) during first 6 months. Methods: From SNUH-DES cohort between August 2003 and December 2004, 98 patients were identified to undergo percutaneous coronary interventions for bifurcation lesions with DES. Patients were divided into two groups; group 1 included 45 patients who underwent DES stenting with SB wire which was jailed after deploying DES, and group 2 included 53 patients who underwent DES stenting without SB wire. We evaluated the difference of angiographic results at 6 months and MACE during first 6 months. Results: Group 1 and 2 did not differ significantly regarding late loss(0.11mm vs 0.10mm, p=0.69) and MACE ( 9.4% vs 6.7%, p=0.46) Conclusion: Jailed SB wire during main vessel DES stenting was not associated with worse late loss of DES at main vessel nor worse clinical outcome. Thus the strategy to freely use SB wire for protection of big SB would be actively adopted in coronary intervention of bifurcation lesion.