In this study we evaluated the effect of the intraoperative irrigation of subarachnoid blood clots in early-stage surgeries for subarachnoid hemorrhages (SAH) in the prevention of hydrocephalus and symptomatic vasospasms. All 25 patients had dense clots exhibiting Fisher groups 3 or 3+4 on a CT scan. The subarachnoid clots were extensively irrigated and washed out in 16 cases (the irrigation group) and minimally removed in 9 cases (the no-irrigation group). Spinal drainage was put into place before the craniotomy, and a trans-lamina terminalis third ventriculostomy was performed for safe retraction of the brain. A urokinase solution was dripped into the subarachnoid space during the subarachnoid dissection for the clotlysis. After the aneurysm was clipped, the clots of the subarachnoid cisterns were irrigated by a high-pressure physiological saline solution buffered by sodium bicarbonate. A 20ml syringe with a locked needle was used to manually inject the irrigation fluids. The occurrence of hydrocephalus and a subsequent need for a ventriculo-peritoneal shunt was 43.8% for patients in the irrigation group and 66.7% for those in the no-irrigation group. The occurrence of symptomatic vasospasms was 12.5% and 77.8%, respectively. In general, outcomes for patients in the irrigation group were better than for those in the no-irrigation group. This is a safe method for the removal of subarachnoid blood clots and results in a better prognosis for SAH patients with thick subarachnoid blood clots.