Aim To investigate the relationship between serum paraoxonase-1(PON-1) and oxidative stress in elderly patients with cerebral infarction and their roles in atherosclerosis. Methods By DSA examination,72 elderly patients with cerebral infarction combined carotid artery atherosclerosis were involved in the study.The light stenosis was seen in 33 cases,the middle stenosis was seen in 24 cases,the heavy stenosis was seen in 15 cases.38 healthy people without cerebrovascular disease were adopted as control group.The activity of serum PON-1 was determined by spectrophotometer.The levels of serum superoxide dismutase(SOD) were detected by xanthine oxidase methods.The levels of serum malondial dehyde(MDA) were detected by thiobarbituric acid reactive substance.We have analyzed correlation between PON-1,SOD and MDA. Results The activity of serum PON-1 and the levels of serum SOD in the cerebral infarction group were significantly lower than those in the control group(95.62±18.26 ku/L vs 168.36±27.82 ku/L,69.59±10.56 ku/L vs 98.34±13.42 ku/L,P><0.01),while the levels of serum MDA in the cerebral infarction group were significantly higher than those in the control group(24.46±5.68 nmol/L vs 15.64±8.26 nmol/L,P><0.01).There were significant differences in the activity of serum PON-1(112.48±19.32 ku/L vs 98.64±10.84 ku/L vs 81.95±13.42 ku/L),the levels of serum SOD(80.62±13.26 ku/L vs 70.26±14.09 ku/L vs 58.82±10.06 ku/L) and MDA(19.52±8.48 nmol/L vs 23.56±9.81 nmol/L vs 27.28±9.89 nmol/L) in the light,middle,heavy stenosis groups(P><0.01).The activity of serum PON-1 and the levels of serum SOD in cerebral infarction group decreased with the progression of carotid artery stenosis,while the levels of serum MDA increased with the progression of carotid artery stenosis.The correlation analysis results showed that there was positive correlation between the activity of PON-1and levels of SOD(r=0.628,P><0.01),while there was negative correlation between the activity of PON-1 and levels of MDA(r=-0.541,P><0.01) in cerebral infarction groups. Conclusion The activity of PON-1 was significantly decreased,while oxidative stress was increased in elderly patients with cerebral infarction.The complicated interaction between oxidative stress and PON-1 may result in occurrence and development of atherosclerosis.