Trigeminal nerve injury is the most problematic consequence of dental surgical procedures with major medico-legal implications. This study reports the signs and symptoms that are the features of trigeminal nerve injuries caused by mandibular third molar (M3M) surgery. 120 patients with nerve injury following M3M surgery were assessed. All data were analysed using the SPSS statistical programme and Microsoft Excel. 53 (44.2%) inferior alveolar nerve (IAN) injury cases and 67 (55.8%) lingual nerve injury (LNI) cases were caused by third molar surgery (TMS). Neuropathy was demonstrable in all patients with varying degrees of paraesthesia, dysaesthesia (in the form of burning pain), allodynia and hyperalgesia. Pain was one of the presenting signs and symptoms in 70% of all cases. Significantly more females had IAN injuries and LNIs (p < 0.05). The mean ages of the two groups of patients were similar. Speech and eating were significantly more problematic for patients with LNIs. In conclusion, chronic pain is often a symptom after TMS-related nerve injury, resulting in significant functional problems. Better dissemination of good practice in TMS will significantly minimize these complex nerve injuries and prevent unnecessary suffering. © 2012 International Association of Oral and Maxillofacial Surgeons.