SummaryPercutaneous coronary intervention for the treatment of a severe calcified lesion is still one of the most technically challenging areas of interventional cardiology. Calcified lesions are a cause of stent underexpansion, which significantly increases the subsequent risks of in-stent restenosis and thrombosis, even when drug-eluting stents are used. In this report, we describe the usefulness of prolonged inflations using a scoring balloon catheter (Scoreflex) for severe calcified lesions. Prolonged inflation using a scoring balloon enables an adequate dilation for treatment of a severe calcified plaque that was unresponsive to conventional technique with or without rotational atherectomy.(Int Heart J 2017; 58: 982-987) Key words: Calcified plaque and indentation, Scoreflex T he use of drug-eluting stents (DESs) reduces the risks of repeat revascularization without an increase in death and myocardial infarction compared with the standard bare-metal stents. However, the risk of in-stent restenosis and stent thrombosis (ST) after DES implantation still remains.Percutaneous coronary intervention (PCI) for the treatment of a severe calcified lesion is still one of the most technically challenging areas of interventional cardiology.