Objective : Cerebral vasospasm is a devastating medical complication of aneurysmal subarachnoid hemorrhage [SAH]. Therefore, prompt detection of vasospasms in aneurysmal SAH is important to the clinical outcome of the patient. For better prediction and effective management of vasospasms, identifying risk factors is essential. This study is aimed at evaluating the relationship between clinical hematologic values, especially white blood cell count, and cerebral vasospasms. Methods : A retrospective review was conducted on 249 patients with aneurysmal SAH who underwent surgical clipping [230 cases] or endovascular intervention [19 cases] between 2003 and 2005. The underlying clinical conditions assessed were leukocytosis, fever, hypertension, diabetes, smoking, Hunt and Hess grade, Fisher grade, aneurysm location, and direct clipping versus endovascular intervention. Results : Two hundred forty-nine patients were treated for aneurysmal SAH during this period. We selected 158 patients in Hunt and Hess grade I - III. Cases of infectious conditions, rebleeding and other surgical/clinical complications were excluded. Vasospasms occurred $7.0{pm}3.1$ days after the onset of SAH. There were several independent predictors of vasospasm : Fisher grade III [p=0.002], fever within two weeks on admission [p<0.001], and a serum leukocyte count >$10.8{ imes}10^3/mm^3$ on admission [p=0.018]. Conclusion : This study results indicate that leukocytosis and fever increase the risk of vasospasms. However, other known risk factors, such as hypertension and smoking, were not correlated with respect to predicting of cerebral vasospasm. Monitoring the serum leukocyte count may be a helpful and useful marker of vasospasms after aneurysmal SAH.