Sleepiness is a common phenomenon in the mid-afternoon, and it causes the so-called 'post-lunch dip' in performance. Recent investigations have demonstrated that a short nap of less than 30 minutes is effective in maintaining daytime arousal. This type of nap has no slow wave sleep and therefore, it is associated with little sleep inertia immediately after awakening. It is pointed out that caffeine, bright lights, music, washing the face, and self-awakening reduces sleep inertia and further enhances the effects of a short nap. (Japanese Journal of Physiological Psychology and Psychophysiology, 25 (1) : 45-59, 2007.)