IVUS-guided PCI has become a standard interventional procedure because IVUS can provide important information not only about vessel diameter and characteristics of plaque but also about stent expansion and apposition, and this information leads to a better prognosis after the procedure. Virtual histology (VH)-IVUS is a unique system to provide plaque tissue typing as four major components using radiofrequency analysis. The necrotic core is the component most related to plaque vulnerability, and plaque that has both NC >10% without evident overlying fibrous tissue and percent atheroma volume >40% in at least three consecutive frames is considered to be VH-thin cap fibroatheroma (TCFA). The PROSPECT trial revealed that VH-TCFA is an important predictor of future coronary events. We investigated which coronary risk factors are related to the amount of NC. Among several factors, AA/EPA ratio is the strongest factor positively related to the amount of NC in both SAP and ACS. Recent studies used VH-IVUS® to elucidate the pharmacological effect of statin on plaque volume and component changes. VH-IVUS® is a unique tool to reveal the pathology and pathophysiology of plaque, and its importance will likely continue to grow.