✓ Intracranial pressure was recorded in 21 patients with subarachnoid hemorrhage due to rupture of a saccular aneurysm. Two different pressure patterns were found in nine patients who had verified recurrent hemorrhages while awaiting clinical improvement. One was associated with massive hematoma while the other occurred with edema but only minimal hematoma; the terms “hemorrhagic-compressive lesion” and “ischemic-edematous lesion” have been used for these two conditions. Four patients showed transient deterioration concomitant with marked pressure peaks in the continuous record. Although there was no evidence of fresh hemorrhage, three of these episodes were followed by a verified hemorrhage within 24 hours. Since no such “warning episode” was seen after the aneurysm had been clipped, the authors consider this pressure peak and concomitant clinical deterioration to be related to the mechanism of aneurysm rupture and possibly a forerunner of a life-threatening hemorrhage. These three pressure patterns showed the whole range from full spatial compensation to total decompensation. The determining factors are considered to be the volume of extravasated blood, the vasomoter reaction, and the intracranial spatial buffering capacity.