Depression and behavioral problems are common in patients undergoing dialysis. Researchers have reported that serum selenium concentrations are generally lower in dialysis patients than in healthy controls. Considerable evidence suggests that selenium deprivation leads to depressed mood, and high dietary or supplementary selenium seems to improve mood. Low plasma selenium concentrations in the elderly are significantly associated with senility and cognitive decline. The author suggests that dialysis-related selenium loss may play a role in biological mechanisms of psychiatric disorders in dialysis patients.