Cerebral anoxia and hypoglycemia of varying severity and diverse causes commonly present neurological problems. Minor transient symptoms are readily diagnosed when they follow insulin injections or operation, but may escape recognition when due to less evident factors, such as hyperinsulinism or paroxysmal cardiac dysfunction. Severe cases with permanent cerebral damage are uncommon but are apt to occur as preventable clinical accidents. It is the purpose of this report to present some clinical and pathological data from a selected group of such severe cases. As preliminary discussion, only brief reference can be made to the vast and scattered literature. The experimental study of anoxia is as old as the subject itself and was of much interest to the philosophers and savants of the 17th and 18th centuries, but the modern era may be said to date from Astley Cooper's1effort to determine the maximum time for which the brain could