Twelve non-psychotic and 13 schizophrenic subjects were given 9 per cent oxygen in 91 per cent nitrogen for 20 minutes without any rebreathing of expired gasses. Neurologic examinations were made at 5-minute intervals during a preliminary control period, the anoxemic period and during the recovery phase. EEG and EKG tracings were recorded and observations made of the pulse rate, respiratory rate, volume of expired air and psychological state at least once each 5 minutes.1. In one patient and one control subject unilateral equivocal plantar responses became definitely dorsiflexor under the administration of 9 per cent oxygen.2. The pupils of the schizophrenic group were smaller than those of control subjects, showed a smaller decrease in size under 9 per cent oxygen, and had a smaller excursion in response to light when tested under anoxemic conditions.3. Consciousness was only slightly affected in any of the 13 schizophrenic patients, but was markedly altered in 3 of the 12 control subjects.Abstract Teaser