A series of 35 patients with 36 giant aneurysms is presented. Thirteen patients presented following subarachnoid hemorrhage (SAH) and 22 with evidence of a space-occupying lesion without recent SAH. The preferred technique of temporary trapping of the aneurysm, evacuation of the contained thrombus, and occlusion of the neck by a suitable clip is described. The danger of attempted ligation in atheromatous vessels is stressed. Intraoperatively, blood pressure was adjusted to keep the general brain circulation within autoregulatory limits. Direct occlusion of the aneurysm was possible in over 80% of the cases. The mortality rate was 8% in 36 operations. Six percent of patients had a poor result. Considerable improvement in visual loss was evident in six of seven patients in whom this was a presenting feature, and in four of seven with disturbed eye movements.