Objective: To study the associations between manganese superoxide dismutase 9Ala/Val(MnSOD 9 Ala/Val) genetic polymorphisms and coronary heart disease(CHD).Methods: The ABI 3100 DNA sequencer was applied to identify the genotype of MnSOD 9 Ala/Val genetic polymorphisms,and colorimeter was used to detect plasma activities of total superoxide dismutase(T-SOD) and MnSOD in 147 CHD patients and 108 controls.Results: Compared with that of controls,the plasma activity of T-SOD and MnSOD reduced obviously,while C-reaction protein(CRP) concentration and intima-medium thickness(IMT) in carotid artery increased markedly in CHD patients.There were more VV genotype and V allele of MnSOD 9 Ala/Val genetic polymorphisms in CHD patients than in controls.The activity of plasma T-SOD and MnSOD decreased,while CRP and IMT increased in individuals with MnSOD 9 VV genotype compared in those with AA genotype,and MnSOD 9V allele correlated negatively with the activity of T-SOD,MnSOD and serum HDL level,positively with fasting plasma glucose,total cholesterol,triglyceride,LDL,systolic blood pressure,IMT and CRP.Conclusion: The antioxidative ability decreased,while inflammatory reaction and degree of atherosclerosis increased in CHD patients.Gene polymorphisms of MnSOD 9 Ala/Val involves in the pathogenesis of CHD by influencing the plasma activities of T-SOD,MnSOD and risk factors of CHD.