NTRODUCTION: Percutaneous coronary intervention (PCI) of Chronic total occlusion (CTO) is remained for challenge. Passage failure of guidewire is still remained most common reason for PCI failure in CTO. Intravascular ultrasound study (IVUS) can give adjuctive informationt o detect the area of occlusion in selective cases from adjacent side branches or from the false lumen and the anatomical information about distals egment of total occluded coronary artery when dye could not penetrate. We report the educational case of successful PCI of CTO of RCA lesion with reverse controlled antegrade and retrograde subintimal tracking and assistance of IVUS. CASE: This case involves 68-year-old man had a history of hypertension, Old myocardial infarction. He was undergone percutaneous coronary intervention (PCI) for LAD, LCX 17 months ago, We performed coronary angiography (CAG) for follow up via right trans radial artery and trans femoral artery approach (bilateral injection) revealed no ISR in LAD and LCX, but showed chronic total occlusion in p-RCA(C,100%,0) with grade III collateral flow. In this case, IVUS study in addition to angiography was performed to evaluate CTO lesions because of previous failure of intervention for proximal RCA. And, we finally considered it was not tapered stump but conus branch. (And it looked as tapered stump.) We pass the wire via septal branch to m-d-RCA (retrograde approach). After successful wiring via retrograde approach (reversed CART) using 2.5mm balloon for p-RCA and m-RCA(C, 95%,III). And then, we deployed 3.5x28mm cypher stent for m-RCA and 3.5x33mm Cypher stent for p-RCA. Final angiogram showed good distal flow without residual stenosis. After PCI, the patients had no complication, such as increased cardiac enzyme, creatinine, chest pain, so we decided that medical therapy and follow up CAG in 6 months later. CONCLUSIONS: If previous attempts to cross the totally occluded lesion from anterograde approach fail, the retrograde approach from collateral should be firstly considered. In futrure, development of IVUS or other diagnostic study would elevate the success rate of PCI with detection of true lumen.