The mechanisms underlying the neurotoxicity of fluorosis still remain obscure. To investigate DNA damage, cell-cycle distribution and expression of nuclear factor kappa B (NF-kappaB) induced by fluoride, the primary rat hippocampal neurons were incubated with various concentrations (20mg/l, 40 mg/l, and 80 mg/l) of sodium fluoride for 24 h in vitro. Our results showed that olive tail moments (OTMs) were significantly elevated in all fluoride-treated groups, while significant increases in the percentage of DNA in the tail were, respectively, observed at 40 mg/l and 80 mg/l levels of fluoride. An increase in the proportion of cells in S-phase was observed in response to the treatment of 40 mg/l and 80 mg/l fluoride. Gene expression of NF-kappaB was also enhanced by fluoride treatment in a dose-dependent manner. The results indicated that fluoride could induce S-phase cell-cycle arrest, up-regulation of NF-kappaB and DNA damage in primary rat hippocampal neurons.