This chapter looks at diseases and conditions of the mouth, lips, and teeth that may present acutely to an emergency department, general practice, or ward. It aims to equip the reader with the necessary knowledge to enable them to quickly and accurately triage and diagnose common clinical problems. Referral pathways and management are also discussed. Generally speaking, patients do not present with a ready-made diagnosis, but rather with either a symptom located to an anatomical region (e.g. toothache, lump, or headache), or an obvious problem (e.g. nose bleed or injury). This is the starting point (‘Common presentations’ and ‘Common problems and their causes’). The next section (‘Useful questions and what to look for’) lists key diagnostic elements in relation to each symptom. The remainder of each chapter details how to examine each site, useful investigations (emergency department and outpatients), and some notes on the conditions themselves. This is a useful aid for the non-specialist and those preparing for clinical examinations.