The main features of atypical facial pain, stomatodynia, atypical odontalgia, and masticatory muscle and temporomandibular joint (TMJ) disorders are compared in this article, which included a search of articles indexed in MEDLINE. The fact that their terminology has been the subject of many debates can be considered a consequence of taxonomic difficulties and uncertainties. Epidemiologic studies indicate marked female predominance for all types of idiopathic orofacial pain. There is also a difference in the age of maximal prevalence between masticatory muscle and TMJ disorders and the other entities. The clinical presentations display several symptoms in common. Pain is oral, perioral, or facial and does not follow a nervous pathway. It has been present for the last 4 to 6 months or has returned periodically in the same form over a period of several months or years. The pain is continuous, has no major paroxysmal character, and is present throughout all or part of the day. It is generally absent during sleep. Clinical, radiographic, or laboratory examination does not reveal any obvious organic cause of pain. There is also a frequent presence of certain psychologic factors, personality traits, or life events. Based on these shared characteristics, a unified concept is proposed. Each of these entities belongs to a group of idiopathic orofacial pain and could be expressed in either the jaws, the buccal mucosa, the teeth, the masticatory muscles, or the TMJ.