Some studies suggested a role for histamine in the pathogenesis of the migraine. So we decided to investigate the histamine-release in two groups of patients: 8 common migraine patients, 8 healthy subjects. Plasma from either controls or migraineurs were mixed with the same control whole blood and histamine release was measured using a radio-enzymatic assay. Migraine plasma induced an histamine release significantly more important than control plasma (p less than 0.01). The nature of an "histamine releasing factor" in the plasma of migraine patient is discussed. This work is an argument for a possible immuno-allergic process in migraine.