Quantitative sensory testing (QST) is a powerful tool to assess pain responsiveness in healthy individuals and patients with orofacial pain conditions and thereby gain insight into the function of the nociceptive system and potential pain mechanisms. In order to appreciate QST and the usefulness of the information for orofacial pain diagnosis and management, it is necessary to understand the basic principles of QST and psychophysics as well as the limitations and potential confounding factors. This chapter briefly reviews the history and some basic aspects of QST in relation to orofacial pain in general and temporomandibular disorder (TMD) pain in particular. Then it presents the highlights and contributions from QST research to the current understanding of orofacial and TMD pain. Finally, it discusses the potential role of QST in diagnosing and determining the prognosis of orofacial and TMD pain.