Prior to root canal therapy, the pulp chamber needs to be accessed to allow mechanical preparation and chemical disinfection of the root canal system. An optimised access facilitates safe and effective endodontic therapy; however, errors during access, in particular over-preparation and under-preparation, may cause problems in subsequent procedures. Detailed understanding of normal anatomy and its variations is imperative and needs to be supplemented with a thorough analysis of the particular case being treated. Odontogenesis and the deposition of tertiary dentine play an important role in determining the location and extent of the penetration into the pulp chamber, as well as the location and trajectory of the coronal root canal portion. High- and slow-speed handpieces with a set of burs along with dedicated hand instruments have been used for endodontic access for decades. More recently, the increasingly widespread addition of the operating microscope and ultrasonically powered instruments has improved the chances of locating orifices, removing mineralisation and optimising access cavities. Locating all present orifices is crucial to the preparation of all canals, and straight-line access, including removal of restrictive coronal dentine and shaping of the coronal third of the root canal, is important for the successful use of nickeltitanium rotary instruments. This review presents the knowledge base and clinical guidelines for safe and efficient access cavity preparation. Schlagwörter: anatomy, endodontic access, instruments, procedural errors