This chapter first highlights the peripheral and central neurobiological mechanisms underlying orofacial pain and then outlines the clinical features of some of the most common or perplexing chronic orofacial pain conditions. Injury or inflammation of peripheral tissues, including nerves, may also lead to phenotypic changes, sprouting or abnormal discharges of the nociceptive afferents and be of pathophysiological significance in certain chronic pain conditions. From the trigeminal ganglion, trigeminal afferents project into the brainstem and terminate on neurons especially in the trigeminal brainstem sensory nuclear complex. Orofacial pain covers a wide range of conditions with different clinical manifestations. Temporomandibular disorders cover an umbrella of common and related pain conditions in the jaw muscles, temporomandibular joint and associated structures. The International Classification of Orofacial Pain divides idiopathic orofacial pain into four different types: burning mouth syndrome, persistent idiopathic facial pain, persistent idiopathic dentoalveolar pain and constant unilateral facial pain with additional attacks.