Total plasma free fatty acids, platelet serotonin content and plasma stearic, palmitic, oleic and linoleic acids were estimated in 10 migraine patients before, during and after a migraine attack. Total and individual plasma free fatty acid levels rose and platelet serotonin content fell in most patients. The highest rise was observed in linoleic acid, which is known to be a potent liberator of platelet serotonin in vitro and is the only precursor of all prostaglandins in the body. It is suggested that the rise in plasma levels of linoleic acid in migraine could be responsible for the platelet serotonin release observed during the attack. At the same time, it may also serve as a source of increased prostaglandin E1 synthesis, which has a powerful vasodilating effect. It is realized that both suggestions have to be confirmed by relevant investigations, as outlined in the body of this paper.