A pair of hypertensive identical twins are reported, one of whom was non-compliant with her antihypertension medication, and after a subarachnoid haemorrhage was found to have multiple cerebral aneurysms. The other asymptomatic compliant twin was noted to have only a single small cerebral aneurysm. As both identical twins are likely to share the same cerebral vascular architecture it is suggested that good control of blood pressure contributed to the cerebral vascular integrity of the asymptomatic twin. This is the first report on the role of blood pressure in the formation of cerebral aneurysms and provides insights for an alternative approach to the controversial management of asymptomatic cerebral aneurysms.