Objective To determine the effect of manganese on Caspase-3 mRNA regulation in spermatogenic cell and the expression of vimentin on Sertoli cell in rat. Methods Forty-eight male rats were randomly divided into one control group and two manganese chloride(MnCl-2)(15mg/kg,30 mg/kg ) groups. After exposed to manganese for 4 and 6 weeks respectively, the apoptosis of spermatogenic cell was examined by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling(TUNEL) technique. The expression of Caspase-3 mRNA in spermatogenic cells was investigated byEM>in situ/EM> hybridization,and the expression of vimentin on Sertoli cell of rats was detected by immunohistochemitry(SABC). Results 1. Compared with control groups, AI was increased(EM>P/EM><0.05，EM>P/EM><0.01)， the Caspase-3 mRNA-positive-cell rate was increased significantly ( P<0.01)， the vimentin-positive-cell rate was decreased significantly(P<0.01) in every manganese exposure groups. 2. Among manganese exposure groups of same dose, AI and the Caspase-3 mRNA-positive-cell rate were increased more significantly, but the vimentin-positive-cell rate was decreased more significantly in 6weeks manganese exposure groups than that in 4weeks manganese exposure groups (EM>P/EM><0.01). 3. Among manganese exposure groups of same time, AI and Caspase-3mRNA-positive-cell rate in 30mg/kg manganese exposure groups were increased more significantly than that in 15mg/kg manganese exposure groups ( EM>P/EM><0.01), but the vimentin-positive-cell rate was decreased more significantly in 30 mg/kg manganese exposure groups than that in 15 mg/kg manganese exposure groups ( EM>P/EM><0.01). 4. There existed a positive correlation between AI and the Caspase-3 mRNA-positive-cell rate (EM> r/EM> =0.842, EM>P/EM><0.01)， a negative correlation between AI and vimentin-positive-cell rate (EM>r/EM>=-0.859, EM>P/EM><0.05)，and a negative correlation between the Caspase-3 mRNA-positive-cell rate and the vimentin-positive-cell rate (EM>r/EM>=-0.975, EM>P/EM><0.01). Conclusion After exposed to manganese the increased expression of Caspase-3 mRNA in spermatogenic cells led to increased apoptosis of spermatogenic cell and decreased express