Abstract: The activities of LDH isozymes were analysed in the hearts, livers, kindneysand brains of SD rats exposed to four different cadmium(Cd) concentrations(0. 2, 0. 4, 0. 8 and 1. 6mg/kg)with poyacrylamide gel electrophoresis. Results:With the rise of the Cd poisonous concentration, the activities of all the LDH isozymes in the hearts significantly increased, whereas, that of all the LDH isozymes inthe kidneys significantly decreased. The activities of LDH1 and LDH2 in the brains increased significantlyfrom 0. 2 to 0. 8 mg/kg Cd and decreased significantly in 1. 6 mg/kg Cd. Cd made significant effects onLDH isozymes in the livers. The results indicated that Cd probably make different effects on the gene expressions of the M and H subunits of LDH isozymes in different organs.