Thirty three subjects diagnosed with Chronic Fatigue Syndrome and 37 healthy matched controls were paired and given either selenium or neutral supplementation to take for six weeks. Blood testing before and after completion of the trials confirmed changes in selenium blood levels. All subjects completed the Profile Of Mood States (POMS) and Beck Depression Inventory (BDI) Questionnaires on three occasions. Mood scores and BDI scores were analyzed and results indicate a marked increase in mood for CFS subjects on selenium compared to CFS subjects on placebo. There was no significant mood change for controls on either treatment. Analysis of the 6 POMS sub-scores also revealed that CFS mood profile was different from the mood profile of healthy controls.