Sixty-nine patients presenting with migraine, with or without aura, after age 40 were investigated with CT or MRI brain scanning, carotid ultrasound and serum antibody studies. A 2:1 female:male predominance was found, the mean age of presentation being 51.6 years. Migraine with aura was reported in 86% of patients. 46% of the females had active menopausal symptoms. No significant haematological or serological abnormalities were detected. CT or MRI brain imaging was normal in 93% of cases; 4 patients had evidence of cerebral infarction. No cerebral tumour or vascular malformation was found. Three patients had evidence of mild-moderate carotid atheroma on ultrasound scanning. Routine detailed investigation of late-onset migraine is unlikely to be of value unless the history is atypical or abnormalities are present on clinical examination.