Abstract: Objective To study effects of chronic cadmium intoxication on apoptosis of epithelial cells of renal proximal tubules.Methods The morphological and structural change of the apoptotic cells of renal proximal tubules of mice exposed cadmium chronically were observed by immunohistochemistry technique(Tunel method)and electron microscopy.The apoptotic cells were counted with image analysis.Results More epithelial cell of renal proximal tubules appeared apoptosis.Apoptotic cells are diffuse or crowded in the epithelium.The cell had the following characters:(1)The volumes of the cells became smaller,and the cytoplasm was concentrated and appeared acidophilic.(2)The nucleoli disappeared and concentrated chro2 matins distributed along the nuclear envelopes.The nucleus looked like a circlet.In later period the nuclei were found pyknosis and were became smaller and compacter.(3)The nuclei appeared karyorrhexis.The apoptotic bodies were seen in some nucle-i.They were covered by the plasma membrane and the shape of them were irregular.They had high electorn-dense and contained broken chromatins and organelles.Compared to the normal control group,the numbers of the apoptotic cells of the renal proximal tubules increased obviously(P<0.01).Conclusion The apoptosis of the cells of the renal proximal tubules were prompted when the mice were intoxicated chronically by cadmium.