Maleimide was used as spin label for studying the effect of hypoxia on rat cerebral cortex neurons.Results showed that hypoxia induced the lipid peroxidation in cerebral cortex cells and increased the formation of LPO. By comparing the characteristics of ESR spectra,it was found that values of τ_c were significantly higher in hypoxic group than that in control(P<0.01).The increase in the ratio of h₀/h_-1 was well correlated with the enhance in hypoxia group. It was also found that MT could inhibit the lipidation in cerebral cortex cells.