The aim of this study was to display the result obtained by the contingent negative variation (CNV) recording in patients suffering from headache. Eighty-five patients were taken into account: 59 with migraines (M) and 26 with tension headache (TH). A typical CNV pattern (high CNV amplitude with no habituation) differentiated M from TH. Moreover, psychological data were collected through Rorschach ink blot test among 42 headache sufferers (31 M and 11 TH). The typical Rorschach repressive pattern of alexithymia was found as well in M as in TH while CNV amplitude was significantly higher in the 31 M (-25 microV) than in the 11 TH (-19 microV FP less than 0.04). Biochemical data collected among 28 patients (17 M and 11 TH) revealed a positive correlation between CNV amplitude and plasma level of noradrenaline, regardless of the type of headache (r = 0.58; P less than 0.01). Thus, besides psychological factors, catecholaminergic mechanisms seem implicated in the determination of the CNV pattern in migraine. CNV may help the clinician both to specify diagnosis and to decide between the many therapeutic strategies available.