Aneurysmal subarachnoid hemorrhage carries a risk of 50% mortality. Therefore it is recommended to also treat asymptomatic, previously unruptured aneurysms. Deciding whether to treat or to observe depends on the consideration of risk of hemorrhage and the surgical risk. Such decision could be facilitated if predisposing factors affecting the outcome were known. 15 Patients with 19 unruptured aneurysms managed in a period when both, surgical and endovascular treatment options were available, were selected from a group of 47 asymptomatic patients documented since 1984. The patients were either operated (n = 9) or were treated by endovascular occlusion with GDC coils (n = 6). In most cases, a long history of headaches eventually lead to a CT-scan or MRI in which a suspicious abnormality was found. Upon subsequent angiography, 8 middle cerebral, 6 carotid, 3 basilar and 1 pericallosal, and ophthalmic artery aneurysm(s), respectively, were found. The aneurysms varied from 4 to 30 mm in diameter. The patients were followed between 9 months and 2.5 years. Treatment results in this small series were independent from size, location, age or sex of the patient. The initial, mostly unrelated symptoms persisted after treatment in most cases. The morbidity according to GOS in this small series (3 out of 19 patients deteriorated) is not representative of the complete series where morbidity and mortality was 5.4% and 1.2% respectively). In agreement with the literature reviewed herein, we recommend surgical treatment of previously unruptured aneurysms, especially when the patients are below 60 years of age. In patients with posterior circulation aneurysms, endovascular coil occlusion is a valid alternative, especially in older patients with concurrent medical problems.