The specific clinical value or relevance of biological markers in orofacial pain conditions is unclear and has been insufficiently investigated. Yet, in addition to the references noted in the previous two chapters, numerous studies are available that indicate highly interesting candidate biomarkers, both molecular and others, for diagnostic or prognostic purposes or to assess or monitor disease activity. These studies provide information about the temporomandibular joint (TMJ), masticatory muscles, oral mucosa, and saliva, as well as details on the clinical neurophysiology of the orofacial somatosensory system. This chapter will focus on recent studies in humans of immunological markers for inflammatory and neuropathic types of orofacial pains as well as neurophysiological biomarkers of orofacial neuropathic pain. Studies of these biomarkers in animals are outlined in Chapters 16-19.