Eleven right-handed females were awakened from REM and NONREM sleep and tested on three tests designed to measure functions attributed to the left hemisphere and on three tests designed to measure right hemisphere function. A significant shift in cognitive profile was found in the direction of right hemisphere dominance after waking from REM sleep, and left hemisphere dominance after waking from NONREM sleep. Comparison of the cognitive shifts in females to that observed in males revealed a significant interaction of gender and awakening condition. Females showed a larger increase in right hemisphere performance following awakening from REM sleep relative to NONREM sleep, and a smaller increase in left hemisphere performance following awakening from NONREM sleep relative to REM sleep. The reverse trend was found for males.