The necessity to remove filling materials from the root canals is one of the major differences between primary endodontic therapy and retreatment. The obturating material has to be removed from the root canals before routine, endodontic therapy can be performed. The removal of the material should not result in a change in the canal morphology, so that the objectives of endodontic therapy can be maintained. Numerous techniques may be used for removing filling materials and other obstructions from root canals. This article reviews the techniques that were suggested in the literature for this purpose and discusses their advantages and disadvantages.