The preparation of an endodontic access is a key step during root canal therapy, particularly for molar teeth. This chapter describes the design and preparation of molar access cavities to facilitate successful endodontic therapy and identify, avoid and overcome potential complications that may arise during treatment. Procedural errors during access significantly reduce the expected outcome for root canal treatment; therefore, detailed knowledge of canal and tooth anatomy and a conscientious instrumentation strategy are required for this step in molar endodontics.