The polycystic disease of kidneys must be considered as a dysplasic lesion and comprised in the large group of enccphalo-splanchnic malformations, one of these being represented by the association of cerebral aneurysms and polycystic kidneys. Many clinical observations tend to show that these two combined lesions have the same congenital and dysplasic character. The arterial hypertension, lately provoked by the anomaly of the kidneys, is only an accessory factor in the development of the associated aneurysms; the rise of blood pressure can however increase the diameter of the aneurysmal pouch and make it burst out. The intracranial hemorrhage is a frequent complication of the polycystic kidneys and often causes the death of the patient long before the development of a severe arterial hypertension. It is known that this cerebral hemorrhage is due, in many cases, to the rupture of an aneurysm. It appears therefore advisable to inquire about every patient with polycystic kidneys, into the existence of associated cerebral aneurysms. Thanks to cerebral angiography, it will be possible to determine the precise seat and to discuss the possibility of surgical treatment of these aneurysms.