The incidence of rerupture during the period of delayed ischemic neurological deficit (DIND) was studied in patients with aneurysmal subarachnoid hemorrhage (SAH) before surgical aneurysmal obliteration, and optimal management of DIND for preventing rerupture is discussed. At Tokai University Hospital, 511 patients with SAH were admitted during the 5-year period from 1988 to 1992. Of these, 247 had not undergone obliteration of the aneurysm neck within 3 days after SAH. In this group, 31% (77 patients) developed DIND. Of these 77 patients, 40 were managed with induced hypertension and/or hypervolemic therapy for DIND (25 with both (group 1), 15 with normotensive hypervolemic therapy (group 2)), and 37 did not receive either kind of therapy (group 3). The incidences of rerupture were as follows: all SAH patients: 11.5%; group 1: 48%; group 2: 7%; group 3: 11%. The incidence of rerupture in group 1 was significantly higher than that in the other groups. On the other hand, the favorable outcome rate (excellent and good) was as follows: group 1: 40%; group 2: 73%; group 3: 22%. This rate was significantly higher in patients who received normotensive hypervolemic therapy, than in other groups. This study suggests that, to avoid rerupture and unfavorable outcome, normotensive hypervolemic therapy is the optimal management approach in patients with DIND after SAH who have not undergone obliteration of the aneurysmal neck.