AIM: To investigate the changes of monoami ne oxidase (MAO), glutathione peroxidase(GSH-Px), superoxide dismutase (SOD ), and malondialdehyde (MDA) in the kidneys of rats exposed to 8 Hz, 130 dB i nfrasound at different times, and to explore the mechanism of kidney injury caus ed by infrasound. METHODS : Thirty-five male SD rats were random ly divided into five groups. Group 1 served as control group, and group 2 to gro up 5 were exposed 2 hours per day to 8 Hz 130 dB infrasound for 1 wk, 2 wk, 3 wk and 4 wk, respectively. RESULTS: MAO activities in all the inf rasound exposed groups increased [(97±28~108±8) nkat·g -1 ], but they s howed no significant difference (P>0 05). GSH-Px activ ities in 4 wk group increased significantly [(181±34~228±24) nkat·g -1 ,[WTBX] P<0 05]. SOD activities remained unchanged followin g exposure to infrasound (. SOD activities remained unchanged followin g exposure to infrasound (P>0 05). MDA concentration i n the 1 wk and 2 wk groups increased significantly[(1 93±0 49~2 55±0 51) μmol·g -1 ,[WTBX]P<0 05], , and it returned to the cont rol level in the 3 wk and 4 wk(1 93±0 49~1 87±0 26)μmol· g -1 . CONCLUSION: The results suggest that the lipid peroxidati on in the kidneys of infrasound exposed rats can be increased and infrasound may play an important role in kidney injury.