The effect of the lavender odorant on a Japanese version of Cox and Mackay's stress/arousal adjective checklist for three groups was studied. One group of 14 was placed into a (2 x 2- x 3 m) sound protected room for 20 min without the presentation of an odor, an analogous group of 15 received the odor oil, and one group of 13 received a nonstressful condition. Analysis suggested that lavender odorants were associated with reduced mental stress and increased arousal rate.