Abstract: ObjectiveTo investigate combined effect of selenium and fluoride on learning-memory behavior of mice and mechanism of brain compared with control group.MethodsSodium fluoride and sodium in deionized water were administered to male mice for 8 weeks.ResultsThe learning ability of higher fluoride groups presented marked deterioration,and the activity of SOD in their brain was lower than control group's(P<0.05).It was found that combined administration of fluoride and proper concentration of selenium could antagonize with this kind of influence of fluoride,it would be synergetic toxicity if concentration of selenium was too high.ConclusionsAll the results suggested that proper concentration of selenium may have ameliorative effects on damages to the learning ability of mice by fluoride,which may be related to activity improvement of SOD in their brain.