We have made an investigation of the 827 cases of ruptured saccular cerebral aneurysms operated on and 151 of them presented infarction attacks thought to be due to vasospasm brought about by aneurysm rupture. Based upon symptoms, angiography and surgical findings, an analysis was made of their age, sex and aneurysm location so related to incidence of infarction, period from the initial or last rupturing until time of infarction, indication of vasospasms from angiographical findings, and symptoms of infarction. Infarction occurs only between the fourth and fifteenth days following the last bleeding and in this period there was a high incidence of rebleeding, so that the current conception of reattack following cerebral aneurysm rupture must be updated in light of the fact that the therapy for rerupture and the therapy for infarction due to vasospasm are completely different.