This paper describes autoregulation in 14 severe closed head injury patients. It was found to be present in eight of the patients. On the basis of these tests, the authors conclude that the presence or absence of cerebral autoregulation may be of prognostic value, the absence indicating a functional loss of cerebrovascular activity. Their findings also indicate that loss of autoregulation combined with an elevated ICP will probably lead to death.THERE IS A CONTROVERSY on whether cerebral autoregulation is present in head injury patients. We have observed that autoregulation is present immediately following severe head injury in unanesthetized baboons. Many authors believe autoregulation is lost in experimental head injury. It may be that autoregulation is lost during the posttraumatic course with deterioration of cerebral conditions.