This study examined the effects of the intensity, quality, and duration of odotogenic pain on the incidence, pattern, and clinical characteristics of pain referral in the orofacial region. Four hundred consecutive patients reporting with posterior toothache to the dental emergency clinic were included. Patients completed a standardized clinical questionnaire consisting of a numerical rating scale for pain intensity and chose verbal descriptors from a list of adjectives describing the quality of their pain. In addition, patients indicated sites to which pain referred by drawing on a mannequin of the head and neck. Pain intensity was found to significantly affect the prsence of referred pain (P .005). However, neither duration nor quality of pain influenced the incidence of referred pain. Finally, pain referral occurred in vertical laminations as indicated on mannequin drawings, but these were not found to be diagnostic because of extensive horizontal overlap. The association of intensity and referral is attributed to central nervous sytem hyperexitability causing expansion of receptive fields and spread and referral of pain.