211 (1), 23-30── The molecular mechanisms of migraine have not been fully clarified yet. Increased nitrosative and oxidative stress may be associated with migraine attacks. Platelets may play an important role in migraine patients and they can reflect the lability of tissues to nitrosative/oxidative stress. In the present study, we aimed to determine the levels of nitrosative and oxidative stress markers in platelets of migraine patients during headache-free and attack periods. A total of 56 subjects (22 migraine without aura, 14 migraine with aura, and 20 age-and sex-matched healthy controls) were included in the study and nitric oxide (NO) metabolites, malondialdehyde (MDA), and thiol (SH) groups were measured in platelets. During migraine attacks, platelet levels of nitrate, nitrite and MDA were significantly higher in migraineurs than these in control subjects (p= 0.042, p= 0.005 and p= 0.042, respectively). By contrast, during headache-free period, no statistically significant differences were found in the platelet levels of nitrate, nitrite and MDA between migraineurs and controls (p> 0.05), although the marginal increases were detected in migraineurs. These results suggest that increased biomarkers of nitrosative and oxidative stress in platelets may be important in migraine patients, especially during attacks; increase of NO metabolites in platelets during attacks supports the opinion that NO may play a modulatory role in biological processes particularly by vasodilatation in migraine attacks. Therefore, MDA and NO metabolites may serve as useful markers to show the increased vulnerability to nitrosative and oxidative stress in migraine patients.──── headache; migraine; nitric oxide; oxidative stress; nitrosative stress© 2007 Tohoku University Medical Press