Previous work has shown that a high fluoride intake in rodents leads to histopathological changes in the germinal epithelium of testes that is associated with zinc deficiency. The purpose of this study was to determine whether supplemental dietary Zn would protect against testicular toxicity induced by fluoride in a small rodent, the bank vole. The 4-month exposure period to fluoride (200 microg/ml of drinking water) induced histopathological changes (hemorrhage in interstitium, necrosis and apoptosis in seminiferous tubule epithelium) which were accompanied by decreased testicular zinc concentration and increased lipid peroxidation. Supplemental dietary zinc (110-120 microg/g) together with fluoride treatment resulted in complete reversal of the fluoride-mediated effects. However, supplemented dietary Zn did not affect the accumulation of fluoride in the testes and bone. These data suggest that a zinc-enriched diet protects seminiferous tubules against fluoride toxicity by preventing the fluoride-induced testicular zinc deprivation.