Oxygen administration coinciding with word presentation enhances word recall in humans, suggesting that elevated levels of circulating blood oxygen may be available to neural memory consolidation processes. This double-blind experiment examined the relationship between blood oxygen levels and cognitive performance when oxygen was inspired for 2 min at different times relative to a simple word recall task, forward digit span and backward digit span. Transient hyperoxia, measured by haemoglobin-bound oxygen, was evident following oxygen inspiration. Neither forward nor backward digit span was affected by oxygen administration. Word recall (12 min following word presentation) was enhanced when oxygen was administered 5 min prior to, immediately before or immediately following word presentation; but not 10 min prior to, 5 min following nor 10 min following, word presentation. These data suggest that oxygen administration can selectively enhance aspects of cognitive performance and support a hypothesis whereby supplemental blood oxygen is sequestered by neural mechanisms involved in memory consolidation.