The author has reviewed a series of 19 patients with unruptured aneurysms treated surgically during a 5-year period from 1976 to 1981. Unruptured aneurysms found in patients with multiple aneurysms and subarachnoid haemorrhage due to ruptured aneurysms are not included in this series. Literature on this subject is reviewed. There was no mortality and results were excellent in 7 patients with asymptomatic aneurysms. In 12 patient with symptomatic aneurysms there was no mortality and results were good to excellent in 9 patients. In 2 the results were unsatisfactory. The series included aneurysms varying in size from 5 mm to over 2.5 cm (giant aneurysm). Controversial aspects of surgery of unruptured intracranial aneurysms are discussed. The authors recommend surgical treatment of unruptured intracranial aneurysms regardless of size until such time when more definitive information is available about the natural history of these lesions.