Background: Success rates for chronic total occlusion (CTO) have notably improved. But, they showed still insufficient success rates for unfavorable anatomical lesions such as stumpless and totally occlusive lesions or occlusion at side branch. We evaluated the clinical feasibility of IVUS-guided wiring technique for these unfavorable lesions. Methods: we enrolled 13 patients with stumpless CTO lesions that were occluded at side branch. We put two guide-wires into main vessel and side branch at each. And then, we placed the IVUS catheter in the side branch and identified the entry points of the main vessel. And then, we pulled IVUS catheter back out of the guiding catheter. We penetrated the CTO lesions with OTW-support. Results: 7 Fr guiding catheters were used in all of the cases. All patients underwent successful reopening of CTO lesions. TIMI 3 flow was achieved in all of the cases. Angiographic results presented at the Table. We used Conquest짰 and Miracle짰 wires to penetrate the CTO lesions. No patients showed PCI-related complication. Conclusion: IVUS-guided wiring technique is useful and safe for unfavorable CTO lesions such as stumpless lesions and occlusion at side branch.