Transdermal scopolamine has been widely used for the prevention of motion-sickness by travelers due to its potent anticholinergic effects and the ease of administration. Nevertheless, its effects on sleep physiology are not known, despite the wellknown fact that the administration of scopolamine as an injection or an oral form could influence the sleep architecture, especially prolonging rapid eye movement (REM) sleep latency and shortening duration of REM sleep. This study aimed to measure the influence of transdermal scopolamine on REM sleep in order to examine whether it affects REM sleep as in the previous studies. We studied eight young healthy male adults polysomnographically for three nights including one adaptation night in a double blind crossover design and compared REM sleep-related variables between sleeps with and without scopolamine patch of 1.5 mg. We found no differences in tonic REM sleep measures such as REM duration and REM latency, but phasic REM sleep measures such as total REM activity (p < 0.05) and total REM density (p < 0.05) were significantly suppressed by the transdermal scopolamine; REM densities of the first (p < 0.05) and the second (p < 0.05) REM sleep periods as well as REM activity of the fourth REM sleep period (p < 0.05) were decreased significantly on the scopolamine patch nights compared with placebo patch nights. These results suggest that phasic REM components reflect cholinergic mechanism in the central nervous system (CNS) even at the lowest commercial dose, and could be useful markers of CNS cholinergic activities in the future research.