Hypertension is a well-known risk factor for the development and rupture of cerebral aneurysms. The authors conducted a study to investigate the prognostic value of admission blood pressure (BP) on prognosis in patients with subarachnoid hemorrhage (SAH). Two hundred patients with SAH were divided into two groups according to Hunt Hess score (good prognosis: 1 to 3, and poor prognosis: 4 and 5) and according to death in hospital (surveyed and died). The prognostic factors of SAH and BP changes according to Hunt Hess scores in the acute stages of the event were evaluated. Admission mean arterial BP values of the patients who died in hospital were significantly lower than in the patients who were surveyed (P=.026). The admission mean arterial BP values were found to be lower in the poor prognostic patients (Hunt Hess score of 4 and 5) (P<.001). Decreased admission BP values were found to be associated with poor prognosis and mortality.