Fifteen consecutive patients with a diagnostic problem of ischaemia-induced migraine with aura (symptomatic migraine) or migraine-associated ischaemia (migrainous infarction) were studied in order to elucidate the mechanisms. Three had a 1 month flurry of daily attacks of migraine auras with or without headache. A severe internal carotid stenosis/occlusion and reduced regional cerebral blood flow (rCBF) was demonstrated. Borderline ischaemia may thus prime the brain for developing migrainous aura with or without migraine (symptomatic migraine). Four patients had a combination of permanent deficits after the very first migraine attack, severe atherosclerosis, risk factors for stroke, high age and no family history of migraine. In these cases the evidence indicates that thromboembolic ischaemia had triggered an attack of migraine with aura (likely symptomatic migraine). Three young females presented long-lasting typical and severe idiopathic migraine with aura. Attack-associated rCBF reduction was likely to have caused permanent, mild, visual or somatosensory deficits (migrainous infarction). In five patients the relationship between migraine and stroke remained unresolved. It seems that ischaemia-induced migraine attacks may be more frequent than migraine-induced ischaemic insults. Therefore, migraine is not as strong a risk factor for stroke as indicated by the mere coincidence of the two disorders.