Traditionally the aneurysms of the circle of Willis have been an indication for neurosurgery. New technologies of endovascular treatment with electrically detachable coils resulted in a different therapeutical concept since four years. A series including 140 patients has been treated in our institution from 1 January 1992 to 31 December 1994, 94 of them presenting with a subarachnoid haemorrhage. Out of these 140 patients, 84 were treated with surgery, 51 with the endovascular technique, five with surgery after incomplete or unsuccessful endovascular treatment. Surgery was indicated in patients presenting early after bleeding, devoid of vasospasm, with a favourable Hunt and Hess grading and in aneurysms located in the anterior part of the circle of Willis. Endovascular treatment was indicated in patients admitted with delay, with severe vasospasm, a poor Hunt and Hess grading and in all aneurysms of the vertebrobasilar arterial network. Age was of less importance in comparison to the status of the vessels for selection of the method of treatment. Giant aneurysms are difficult to treat as surgery is faced with the size of the aneurysmal itself and endovascular technique with the width of the aneurysmal neck.