1H-NMR spectroscopy and patte recognition (PR) method were used to assess the acute biochemical effects of light rare earths.Male Wistar rats were treated with both La(NO3)3 and Ce(NO3)3 at doses of 2,10,and 50 mg/kg body weight.Serum samples from the rats with the two kinds of doses of light rare earths were obtained after 48 h and analyzed by a 600 MHz 1H-NMR spectrometer.Each NMR spectra was data-processed to provide 238 intensity-related descriptors as input coordinates in a multidimensional space and analyzed by PR method.Many low-molecular weight metabolites were identified by 1H-NMR spectra of the rat serum.An increase in ketone bodies,creatinine,lactate,succinate,and various amino acids (valine,leucine,and glutamine)were found from the higher doses (10 and 50 mg/kg body weight) of rare earths-treated groups,together with a decrease of glucose in the serum from Ce(NO3)3-dosed groups.These findings may mean that high-dosage of La and Ce impair a specific region of liver.The similar toxicities with various mechanisms for La and Ce are implicated by NMR-based metabonomic approach.Ce(NO3)3 exhibited a higher toxicity than La(NO3)3 at the same doses.