The ability to provide painless and effective local anaesthesia is a critical aspect of pain control in dentistry. The success of any practice is at least partly dependent on the reputation of the dentist in terms of delivering painless injections. Mandibular anaesthesia is important for two reasons: anaesthetic failures are most common in this region; and, postinjection complications are more frequently associated with mandibular anaesthesia. In this regard, assessment of the patient should focus in part on identifying previous difficulties with local anaesthesia. Possible problems might include failure to achieve satisfactory local anaesthesia, an unreasonably brief duration of anaesthesia, or significant postoperative pain or stiffness.