We demonstrate an immediate effect of airborne chemicals on human moods. We collected six groups of underarm odors, respectively, from five prepubertal girls, five prepubertal boys, five college women, five college men, five older women, and five older men. In addition, we collected odors from homes of these donors, making them a seventh group of odor. Three hundred and eight odor observers ranked the seven groups of odors of little girls, little boys, college women, college men, older women, older men, and homes by their perceived pleasantness, intensity, perceived masculinity, and age of the donors, among other qualities. On a separate task, the same odor observers assessed their depressive, hostile, and positive moods twice, once before and once a few minutes after they sniffed one of the above seven groups of odors. Exposure to underarm odors for under 2 min led to significant, rapid, and small changes in the nonclinical depressive mood of the odor observers. The mood changes were independent of the observers' perceptions of odor qualities. Odors perceived as unpleasant and intense were as likely to relieve a depressive mood as were pleasant odors.