Eleven healthy men were confined in a metabolic research unit for 120 days in a double-blind study of the effects of dietary selenium on mood as assessed by the Profile of Mood States-Bipolar Form. At an intake of 2800 kcal/day, the diet of conventional foods provided 80 micrograms/day of selenium for the first 21 days, then either 13 or 356 micrograms/day for the remaining 99 days. There were no significant changes in any of the mood scales due to dietary selenium. However, in the low-selenium group, the changes in the agreeable-hostile and the elated-depressed subscales were correlated with initial erythrocyte selenium concentration; that is, the lower the initial selenium status, the more the mood scores decreased. These results suggest that persons with low selenium status might experience relatively depressed moods and support the idea that selenium plays a special role in the brain. However, these studies do not support the notion that selenium supplementation could promote improvements in mood in persons eating a typical U.S. diet.