BACKGROUND Systemic autonomic changes are well known in migraineurs. Also, masticatory disorders are reported to be associated with migraine. However, if those phenomena are interrelated, and how, is unclear. Moreover, the knowledge on the autonomic responses to masticatory stimuli in migraineurs is limited. OBJECTIVE To investigate tooth clenching-related cardiac autonomic regulation in migraineurs. METHODS We compared maximal tooth clenching-induced systemic autonomic responses, indicated by heart rate variability and blood pressure changes, in headache-free migraineurs (n = 17) and control subjects (n = 22). RESULTS Levels of high-frequency power, reflecting vagal activity, were lower in migraineurs at baseline but increased after tooth clenching whereas in controls they returned to baseline (P