A series of 55 patients with ruptured cerebral aneurysms were treated with moderate removal of subarachnoid clot followed by intracranial irrigation with pH 8.0 Hartmann solution containing 1 mg/ml of methylpredonizolone sodium succinate after the aneurysmal clipping during early (before day 3) operation. Six (11%) of the 55 patients suffered vasospasm syndrome postoperatively. The clinical results are significantly better than a series of 68 patients operated on and treated before day 3 by intracranial irrigation with Hartmann solution (pH 8.0) only. The possible preventive effect of direct intracranial administration of steroid hormone is discussed.