Several authors have used transcranial Doppler studies (DTC) in the study of changes occurring in migraine. They found an increase in mean velocity (VM) as compared with controls. However there are few studies of this in tension headache.To determine possible differences in VM and pulsatility index (IP) between patients with migraine and those with episodic tension headache by means of DTC.We studied 26 patients with migraine, 30 with episodic tension headache (criteria of the IHS) and 21 controls using DTC (Multi Dop P/TCD DWL). We determined the VM and IP of the middle cerebral arteries at a depth of 50 60 mm. Uni bivariate statistical analysis was done using the computer programme SPSS.The VM were: 75.92 cm/s in migraine; 65.96 cm/s in episodic tension headache and 72.28 cm/s in the control group (the differences were not statistically significant: NS). The IP were: 0.80 in migraine and 0.76 in control and tension headache groups (NS). No differences were found either when the VM of migraine and tension headache were compared directly (p=0.067). The theoretical number of patients necessary for a study with results giving statistically significant tendencies was calculated as 44 in each group.1. No statistically significant differences were found, probably due to lack of statistical power, since the migraine group showed a tendency to a higher velocity. 2. Further studies on larger numbers of patients are necessary to evaluate the differences between migraine and episodic tension headache.