Objective To have a knowledge about relations between senile coronary heart disease and nitric oxide（NO） as well as nitric oxide synthase（NOS） and the clinical significance thereof.Method 154 elderly patients with coronary heart disease were chosen for the research group and 106 healthy ones formed the control group.The NO and NOS content of the two groups were determined respectively

and the results were compared and analyzed.Results For the group with senile coronary heart disease and the healthy control group

the content of serum NO was（62.51±15.36） mol/L and（89.31±17.26）mol/L respectively while the NOS content was（8.26±5.98） and（13.45±6.24） respectively

and each content in the group with senile coronary heart disease was lower than that in the control group（P<0.05 or P<0.01）.Conclusion The contents of NO and NOS in elderly patients with coronary heart disease are obviously lower compared with those of the healthy ones

which was probably a dangerous factor causing coronary heart disease.