A study was conducted to examine the vestibular ocular reflex (VOR) during narcosis. The slow phase velocity of the nystagmus was measured in six subjects by means of electronystagmography during the inhalation of 25% nitrous oxide. It was found that nitrous oxide increased the velocity of the slow phase component of the VOR by approximately 50%. This result indicates that the gain of the VOR is effectively increased during nitrous oxide induced narcosis. It appears that the vestibular end organs and/or the central pathways controlling nystagmus are affected by nitrous oxide and this may be a reason for the disruption in balance associated with inert gas narcosis.