The headache profile of idiopathic intracranial hypertension (IIH, pseudotumour cerebri) has not previously been prospectively studied. We administered a questionnaire to 63 cases at the time of diagnosis. Fifty-eight of the cases had headache and 93% of those with headache reported it to be their most severe ever. Patients characteristically noted a pulsatile headache of gradually increasing intensity that had awakened them. Daily headache occurred in 74% of those reporting headache. Pain in a nerve root distribution or retro-ocular pain with eye movement, uncommon with other headache disorders, help to differentiate this headache syndrome.