Abstract: Objective To study the apoptotic effect of cadmium chloride on anterior pituitary and adrenal cortex and the relations with caspase-9 signal transduction passway.Methods 40 SD male rats were randomly distributed into four groups which were administerd with CdCl₂ at different doses by gavage for 6 weeks.The indices included:detection of apoptosis of anterior pituitary and adrenal cortex with electronic microscope,TUN EL assay,expression of procaspase-9 mRNA and caspase-9.Results Apoptosis inclined to enhance remarkably,and the expression of procaspase-9 mRNA and caspase-9 appeared to be increased significantly as compared with those of the control.It was shown that a dose-effect relationship between the CdCl₂ dosage and indices above with the regression analysis and a linear correlation between the mean gray value of apoptosis cell and the level of procaspase-9 mRNA and caspase-9.Conclusion Cadmium could induce apoptosis of anterior pituitary and adrenal cortex in the manner of dose-dependent,and caspase-9 might play a role during above processes.