The metabotropic glutamate receptors (mGluRs), as one of the newly found glutamate receptors, play an important role in the physiological processes of the central nervous system. The authors examined the changes of expression patterns of mGluRs after diffuse brain injuries (DBI) in rats. DBI was produced by Marmarou's methods. The mRNA expression of mGluRs was detected by hybridization in situ at different time points after brain injuries. Compared with normal control and sham-operated control, the animals with DBI showed a significantly increased expression of group I and group III mGluRs (except mGluR6, P<0.05). The increased peak of group I appeared at 24 h after injuries and group III at 6 h after injuries. While, group II mGluRs decreased after DBI (P<0.05) and the lowest point occurred at 48 h after DBI. The difference of time sequence of the expression alterations between group I and group III mGluRs may reflect a self-protection first mechanism of the damaged neurons. It may provide new insight for the development of new pharmaceuticals in the treatment of DBI.