We investigated some ultrastructural aspects of platelet activity in patients with classic migraine during an attack-free period. We focused on the production of malondialdehyde (MDA), the intracellular concentration of Ca++ and the membrane phospholipid structure using a DPH (1,6 diphenyl-1,3,5 hexatriene) fluorescent probe. Our study comprised 20 patients with classic migraine and 5 healthy controls, from whom 10 cc samples of blood were collected in test tubes containing sodium citrate (1/9 cc). We found no significant differences in MDA production between migraineurs and controls either before or after stimulation with thrombin. The same applies to the concentration of intracellular Ca++ (Ca++i). The membrane lipid composition assessed by DPH fluorescent probe was normal both in migraineurs and in controls. Our findings suggest no intrinsic activation of platelet aggregation.