Background: Recanalization of the chronic total occlusion(CTO) has notably been improved as new devices and technologies are introduced. However,the procedural success rate is still not acceptable for anatomically unfavorable lesions such as stumpless CTO. The intravascular ultrasound(IVUS) is useful for the identification of the entry point of the CTO and the evaluation of the lesion characteristics such as plaque composition and calcium deposition. We investigated the clinical feasibility of IVUS-guided wiring technique for the CTO lesions with no visible stump. Methods: Thirty lesions of twenty nine patients(M/F=23/6 ; mean age=61.4짹8.8) were enrolled from Jan 2005 to July 2008. Seven Fr guiding catheters were used in all cases. After putting the guide-wire into side branch, the IVUS catheter was introduced into the side branch for the identification of the entry point of the main occluded vessel. The stiff guide-wires such as Miracle짰 series or Confienza짰 were navigated into the ostium of the CTO under IVUS guidance. After the guide-wire was engaged into the ostium of the CTO, the over-the-wire balloon(OTW) was introduced into the guide-wire for strong support and wire exchange. We changed guide-wire through the OTW step by step up to the confienza짰 pro 12 gram with confidence until the guide-wire passed the full CTO lesion. Results: The occlusion site was LAD in 21 lesions, in the LCX in 1 lesion, and in the RCA in 8 lesions. The mean lesion length and the mean stent length were 34.1 짹15.3mm and 37.5짹17.3mm, respectively. The CTO lesions were successfully reopened with final TIMI 3 flow in 24 lesions (80%). The procedure was failed in six cases. Two lesions had severe osteal calcification that hindered wire penetration. Slow flow was developed in two cases. In another two cases, coronary perforations were occurred, however pericardiocentesis was not needed. There was no clinically significant PCI-related complication. Conclusion: IVUS-guided wiring technique is useful and safe for stumpless CTO lesions.