Apical extrusion is inevitable during root canal instrumentation and a methodology that completely avoids this phenomenon has not yet developed. Despite strict length control of the endodontic instruments during root canal preparation, the dentinal filings, pulp tissue fragments, necrotic tissue, microorganisms, and the intracanal irrigant might get extruded from the apical foramen into the periradicular region resulting in interappointment flare ups and post operative pain. This book gives the overview in relevance of apical extrusion in endodontics from a clinical and biologic perspective