To investigate the comorbidity of premenstrual syndrome (PMS) and menstrual migraine, the Menstrual Distress Questionnaire (MDQ) was prospectively administered for two consecutive menstrual cycles to 22 patients with menstrual migraine, 12 cases with migraine without aura and 15 patients with PMS. MDQ scores varied throughout the menstrual cycle in each patient group, the wider changes being shown by patients with PMS. Fourteen menstrual migraine patients and 4 migraine without aura patients achieved diagnostic criteria for PMS over two menstrual cycles. In these patients MDQ scores did not differ from PMS sufferers at any stage of the menstrual cycle. The premenstrual increase of each cluster of PMS symptoms was identical in menstrual migraine and PMS subjects with the exception of negative affect. We suggest that PMS symptoms should be taken into account in the IHS diagnostic criteria for menstrual migraine.