Of 250 patients admitted with aneurysmal subarachnoid hemorrhage (SAH) from 1994 to 2000, 16 had massive intra-sylvian hematomas. To predict the useful determinants of the clinical outcome for such patients we analyzed our last 16 cases. The study was performed in 2 parts. Part 1 covered the period from 1994 to 1996 and included 5 patients who underwent early surgery. Immediately before operation, Hunt & Kosnik grade (H&K) III was observed in 1, IV in 3 and V in 1 patient. Part 2, from 1997 to 2000, included 11 patients who underwent ultra-early surgery (within 3 hours after admission) with ventriculostomy and with 2 weeks' postoperative management in the ICU. Preoperatively, there were 2 patients with H&K III, 7 with IV, and 2 with V. The results in part 1 showed that 3 out of the 5 patients had poor outcome with symptomatic vasospasm. While in Part 2, seven returned to work, 2 had minimal and 1 had severe neurological deficits with symptomatic vasospasm, and 1 died. We therefore suggest that ultra-early surgery with ventriculostomy and postoperative management in the ICU is the most useful determinant to improve the clinical outcome in the treatment of SAH patients with massive intra-sylvian hematoma.