Neurofilaments (NFs) are hyperphosphorylated and accumulate in Alzheimer's disease (AD) brains. In this study, employing the transgenic mouse model, we explored the effect of presenilin 1 (PS-1) mutation on the phosphorylation and distribution of NFs. Western blot analysis showed that there was a significant increase in the phosphorylation of NF-H and NF-M subunits with a concomitant increase in phosphorylated c-Jun N-terminal protein kinase 1/2 (JNK1/2) mitogen-activated protein kinase (MAPK) in hippocampus of PS-1 transgenic mice compared to that of wild-type littermates. Immunohistochemical analysis revealed that phosphorylated NFs accumulated throughout the hippocampal neurons of the transgenic mice. These findings suggest that PS-1 mutation may induce hyperphosphorylation and accumulation of NFs via a JNK1/2-involved mechanism.