A current hypothesis for migraine suggests that neuroexcitatory amino acids may participate in the triggering of attacks. To investigate this possibility we measured glutamic and aspartic acid level in plasma and cerebrospinal fluid (CSF) of patients with common and classic migraine during attacks, making comparisons with controls suffering stress. Plasma levels of amino acids in migraine patients were lower than in controls. CSF concentrations of glutamic acid were higher in migraineurs than in controls. Our results suggest an excess of neuroexcitatory amino acids in the CNS of migraine patients during attacks, possibly favoring a state of neuronal hyperexcitability.