The bioeffects of Changle, a rare earth complex on rats were investigated using NMR and ICP techniques. Wistar rats were administrated orally with Changle (a rare earth-containing fertilizer additive applied in agriculture to raise the production of crops) at doses of 2, 5 and 20 mg·kg-1 body weight/day respectively for 90 d. The urine of Changle-treated rats was collected at 45 and 90 d and serum samples were taken after 90 d. The relative concentrations of some important endogenous metabolites in biofluids were determined by 1H NMR spectra and the contents of the four rare earth elements (La, Ce, Pr and Nd) constituting Changle in the serum samples were measured by ICP-MS technique. Changle-induced renal and liver damage is demonstrated based on the increase in the amounts of the amino acids, trimethylamine N-oxide, N, N-dimethylglycine, dimethylamine, succinate, α-Ketoglutarate ethanol and the alteration of rare earth concentrations in serum.