Endodontic nonsurgical retreatment is a comprehensive field. This field of endodontic has its own science, literature, specific technologies, best materials, and escalating range of techniques that are, at times, required to achieve clinical success. It may be divided into the following categories: coronal disassembly, locating previously missed canals, removing obturation materials, negotiating blocks, bypassing ledges, managing transportations, repairing perforations, treatment planning fractures, and removing posts and broken instruments. However, not all failures are amenable to successful nonsurgical retreatment. Clinicians need to weigh risk versus benefit and recognize that, at times, a referral, surgery or extraction might be in the patient's best interest. Properly performed, endodontic treatment is the corner-stone of restorative and reconstructive dentistry.