Ninety-six male Kunming strain mice (19-21 g b.w., aged 7 weeks) were obtained from the Academy of Military Medical Science (Beijing, China). After seven days adaptation, mice were allotted randomly into four groups (24 mice each). A control mice group got distilled water. Three experimental groups were treated with 50, 100 and 150 mg/L fluoride (NaF) in mice drinking water. During the experimental period, experimental groups had free access to water and standard feed. After 12 weeks of NaF exposure, all four groups were tested for learning and memory abilities by Ymaze test. After 90 days of NaF exposure, mice were sacrificed by cervical dislocation. The femur of mice was stripped and stored at room temperature for analyzing the content of bone fluorine by the method of fluoride ion-selective electrode. Laboratory conditions for animals were at 22-25 C, 12-hr light/dark cycle. All procedures in this study were approved by Institutional Animal Care and Use Committee of Shanxi Agricultural University.