We studied the plasma levels and cerebrospinal fluid (CSF) levels in twenty-nine patients suffering from migraine without aura and in eighteen others with aura. The samples were obtained during migraine attacks. We compared the results obtained with those from twenty-seven control subjects. Histidine levels in plasma were 1.18 +/- 0.51 mg/dl for the control group, 1.75 +/- 0.39 mg/dl in those suffering from migraine without aura and 2.07 +/- 0.64 mg/dl in those cases of migraine with aura. In both plasma and in cerebrospinal fluid concentrations of histidine were greater in patients with migraine than in controls (p < 0.001). Histidine is an amino acid precursor of histamine and its abnormalities may be demonstrative of the participation of this amine in migraine attacks, possibly within the state of neuronal hyperexcitability.