Hydrocephalus is not a rare complication following aneurysmal subarachnoid hemorrhage. Hydrocephalus following subarachnoid hemorrhage can progress acutely (0-3 days), subacutely (4-13 days) or chronically (after 13 days). The predisposing factors leading to hydrocephalus after subarachnoid hemorrhage are not known exactly. This study assessed the predictive factors for the development of this condition. All patients presenting with subarachnoid hemorrhage between 1992-2001 were evaluated. All of them had initial computed tomography (CT) and hydrocephalus was diagnosed on CT scans. Age, gender, preexisting diabetes mellitus and hypertension, neurological state according to the Hunt and Hess scale at admission, Fischer grade on CT, the presence of intraventricular hemorrhage and localization of aneurysm were analyzed to see if there was any meaningful relationship between hydrocephalus and these factors. One hundred and fourteen patients with aneurysmal subarachnoid hemorrhage were evaluated. The incidence of hydrocephalus was 28.1 %. The incidence for acute hydrocephalus was 18.4 %, for subacute 5.2 % and for chronic 4.3 %. Sixty-nine percent of patients with hydrocephalus were graded as 3, 4 or 5 according to the Hunt and Hess scale on admission. Fifty-five percent of patients with hydrocephalus were graded as 3 and 4 according to Fisher grade on initial CT scan. Preexisting diabetes, higher Fisher grade and intraventricular hemorrhage were statistically significant predictors for the development of hydrocephalus. But only preexisting diabetes and higher Fisher grade were independent predictors according to multivariate analyses.