Patients in poor grade (WFNS IV and V) after aneurysmal subarachnoid hemorrhage (SAH) often have a bad outcome. To evaluate early GDC embolisation on such patients a prospective observational study, with comparison to a historical cohort was performed. From January 1996 to December 1998 113 patients were admitted to the Department of Clinical Neurosciences in poor grade after SAH (45 WFNS IV and 68 WFNS V). Eighty-one patients were managed actively with endovascular occlusion of the aneurysm (n=42) where possible and delayed clipping (n = 16) where not. On an intention to treat basis, 46% had a favourable outcome (Glasgow Outcome Score IV or V) and 48% had died by 3 months. Compared to an historical cohort managed in the same unit between 1992 and 1995 (n = 62, 52% favourable outcome) these results suggest that early GDC aneurysmal occlusion has had a minimal impact on overall outcome. (C) 2002 Elsevier Science Ltd. All rights reserved.