This chapter covers immunological markers for inflammatory types of temporomandibular joint (TMJ) pain. The specific biological relevance or clinical value of biomarkers in TMJ pain is, however, so far insufficiently investigated. There are studies that indicate candidate biomarkers for diagnostic or prognostic purposes in diseases like rheumatoid arthritis and psoriatic arthritis. This chapter discusses available knowledge regarding cytokines, cytokine receptors, serotonin, prostaglandin E2, and glutamate in relation to diagnosis, prognosis, and treatment of TMJ inflammatory pain.