240 patients with giant aneurysms admitted to 10 Italian centres were evaluated in regard to results of treatment and postoperative complications. As a whole, a complete recovery was observed in 39% of cases, various degrees of disability in 38% of cases, and death in 23% of cases, considering also patients admitted in Glasgow Coma Scale (GCS) 3-6. By excluding patients in GCS 3-6, active treatment was linked with a recovery rate of 47% and a mortality rate of 15%; the worst outcome was observed for carotid bifurcation aneurysms, the best for intracavernous aneurysms. In patients with giant carotid/ophthalmic or supraclinoid aneurysms, the outcome was similar after early surgery and after indirect methods of treatment. Factors playing a negative influence on outcome were mainly early exclusion after hemorrhage, operative brain swelling and cisternal tamponade; induced hypotension was associated with a significant decrease in mortality. Postoperative complications were observed in 48% of cases, and were mainly caused by ischaemic disturbances not associated with vasospasm (17% of cases), followed by surgical trauma and cerebral oedema; in 32 patients the postoperative neurological deterioration was fully reversible. In patients submitted to carotid occlusion association with a by-pass did not decrease the rate of ischaemic complications. In patients submitted to active treatments (open surgery or indirect methods of exclusion) the causes of morbidity were mainly: -deficits due to mass lesion, surgical complications, and ischaemic disturbances without vasospasm; the causes of mortality were mainly surgical trauma or medical complications.