With the widespread application of drug-eluting stent(DES)technology and rapid advancement in stent bioengineering,the efficacy and safety of percutaneous coronary intervention(PCI)have significantly improved.Howev-er,the incidence of in-stent restenosis(ISR)remains a critical issue,with approximately 1％to 2％of patients requiring repeat revascularization annually.Given the global implantation of millions of DES each year,ISR has emerged as a major clinical challenge demanding urgent resolution.The pathological mechanisms underlying DES-ISR are complex and heter-ogeneous,and with continuous progress in intracoronary imaging techniques,these mechanisms and classifications have been further elucidated.Concurrently,therapeutic tools and strategies for ISR are undergoing ongoing development and optimization.This review summarizes recent research progress and achievements in the definition,classification,patho-logical mechanisms,imaging characteristics,and treatment approaches related to DES-ISR.