OBJECTIVES: This study aimed to determine whether side branch (SB) wire jailing before main vessel (MV) stenting could prevent SB occlusion after the 1-stent strategy for bifurcation percutaneous coronary intervention. BACKGROUND: The benefits of SB wire jailing in the 1-stent strategy remain unclear. METHODS: From the COBIS (Coronary Bifurcation Stenting) III registry, 1,890 patients with bifurcation lesions who underwent the 1-stent strategy using second-generation drug-eluting stents were identified and classified into 2 groups according to the use of SB wire jailing: wire jailing (n = 819) and non-wire jailing (n = 1,071). The incidence of SB occlusion (Thrombolysis In Myocardial Infarction flow grade <3) and target lesion failure (cardiac death, myocardial infarction, or target lesion revascularization) was compared. RESULTS: The incidence of final SB occlusion was not significantly different between wire jailing (1.8%) vs non-wire jailing (2.9%; P = 0.182). However, wire jailing at the SB was a significant protective factor for SB occlusion after MV stenting on multivariate analysis and was significantly associated with a lower incidence of SB occlusion in patients with significant stenoses (>/=60%) at the SB (5.1% vs 11.3%; odds ratio: 0.42; 95% CI: 0.19-0.89; P = 0.028) or MV (3.1% vs 6.2%; odds ratio: 0.49; 95% CI: 0.24-0.95; P = 0.039). During follow-up (median 52 months), the incidence of target lesion failure was not significantly different between wire jailing and non-wire jailing (7.6% vs 6.3%; P = 0.343). CONCLUSIONS: During bifurcation percutaneous coronary intervention with the 1-stent strategy, wire jailing at the SB was associated with a lower rate of final SB occlusion following MV stenting in patients with severe stenoses at the SB or MV but not with overall bifurcation lesions. Long-term clinical outcomes were comparable between the 2 groups.