This study was undertaken to elucidate comprehensively the serial changes occurring in hemostatic systems after aneurysmal subarachnoid hemorrhage (SAH) and thereby to ascertain whether the examination of the integrity of these systems is helpful in predicting delayed ischemic neurological deficits (DINDs). The authors examined 117 patients admitted to the hospital within 24 hours after onset of SAH. Blood samples were collected from each patient on Days 0 (at admission), 3, 6, 14, and 30. A number of hemostatic parameters were examined in these samples, and the relationships between their changes and DINDs were assessed. Eighteen (15.4%) of the patients exhibited DINDs, and their frequency increased as the severity of subarachnoid clotting increased. Also, the frequency of DINDs was significantly higher in the patients with hydrocephalus on initial computerized tomography (CT) scans than in those without hydrocephalus. Regarding the hemostatic parameters at admission, there was no significant difference between the patients with and without DINDs. On Day 3, however, the fibrinogen and D-dimer levels were higher in the patients with than in those without DINDs. The fibrinogen and thrombin-antithrombin complex levels on Day 6 and the D-dimer level on Day 14 in the patients with DINDs were higher than the corresponding levels in those without DINDs. Multivariate analyses revealed that the following variables (in order of importance) were independent predictors of DINDs: the levels of D-dimer on Day 3, fibrinogen on Day 6, and the presence of hydrocephalus on admission. These data indicate that the levels of hemostatic parameters in concert with the CT findings may enable us to predict the appearance of DINDs.