The effect of cisternal drainage and intrathecal urokinase (UK) injections in preventing symptomatic vasospasm after aneurysmal subarachnoid haemorrhage was retrospectively studied in 69 patients with uniform backgrounds with regard to subarachnoid haemorrhage (SAH; WFNS grade I to IV, Fisher's group 3, undergoing surgery or coil embolization within 72 h of the onset). With regard to the selection of patients, 34 patients belonging to the control group (no UK injection group) underwent the treatment during the 3-year period from 2001 to 2003, while 35 patients belonging to the UK group underwent the treatment during the 3-year period from 2004 to 2006. The incidence of symptomatic vasospasm was 5/35 with the UK group, but 12/34 with a control group. The UK injection significantly reduced the incidence of symptomatic vasospasm (p = 0.042, Pearson chi-square test), resulting in an improvement shown by the Glasgow Outcome Scale (GOS; p = 0.030, Mann-Whitney U test; Table V). The distribution on the angiographic grading scales for cerebral vasospasm significantly shifted in a positive direction for the UK group (mild 0, moderate 5, severe 0) in comparison with the control group (mild 0, moderate 4, severe 8; p = 0.014, Mann-Whitney U test). This study suggests that combining continuous cerebrospinal drainage and intermittent intrathecal UK injection therapy is a relatively simple and effective method for symptomatic vasospasm prophylaxis in patients with aneurysmal SAH.