The authors analyze a series of 53 patients who presented with unruptured intracranial aneurysms. Fifty were operated upon, 2 died during the post-operative period, 5 were left with their pre-operative neurological deficit, 43 were cured and have not subsequently presented with any cerebral or meningeal haemorrhages. None of the 3 patients who were not operated upon has since presented with a cerebro-vascular accident. Twenty-five aneurysms were asymptomatic, discovered fortuitously during angiographic examination, and their size was generally between 3 and 6 mm. Twenty-eight aneurysms presented with various neurological signs and symptoms (headaches, facial pain on 9 occasions, ischaemic vascular accidents on 7 occasions, ocular signs on 8 occasions and generalized epilepsy on 4 occasions), with a range in size from 7 to 10 mm. The clinical and autopsy series published in the literature show the usefulness of surgery when certain factors come together and increase the risk of rupture: middle-aged patients (between 40 and 65), arterial hypertension, aneurysm located on the anterior part of the circle of Willis and with a diameter close to the critical size (10 mm) for rupture.