One of the major controversies in root canal concerns the apical limit of instrumentation and obturation. A number of anatomical histological studies have been carried out to determine the true termination of the root canal. The apical extent of the cleaning and shaping procedure and also of the obturation material is a topic that has resulted in much controversy in endodontics. Patency filing is a newer concept in endodontics which has been stressed by a number of authors and researchers. This article discusses the concept of patency and its necessity in endodontic therapy.