Fifty cases of verified intracranial ruptured saccular aneurysm were analyzed to investigate the relationship of the development of a delayed cerebral ischemic deficit to the presence of cerebral vasospasm visualized on angiography. Twenty-five patients developed a delayed ischemic deficit (DID), and all showed Grade 3+ or 4+ vasospasm. Nineteen patients had Grade 0, 1+, or 2+ vasospasm, and none developed a DID. It was concluded that in this study vasospasm accounted for all DID's and that in the absence of vasospasm DID did not occur. The DID occurred most often on Day 8 (7 of 25 cases).