The levels of nitric oxide（NO）synthesis were measured by a copper-coated cadmium reduction method in human serum and bronchial washing fluid（BWF）from 25 patients with Lung cancer（LC）

14 patients with benign pulmonary disease（BPD）and 18 normal controls（NC）

along with the correlation between NO and Tlymphocyte subpopulation in BWF.Results:Serum NO level in patients with LC and BPD were significantly higher（P

<

0.01） than those in NC

but there were no significant difference（P

>

0.1）in patients with LC and BPD.The levels of BWF NO in patients with LC were significantly higher（P

<

0.01）than those in patients with BPD.The BWF levels of NO had postitive correlation with serum levels of it in LC patients（P

<

0.01）.No correlation could be found in BPD patients and NC

In TNM stages Ⅰ to Ⅳ of patients with LC

the levels of NO stages Ⅲ and Ⅳ were significantly higher（P

<

0.01）than those in the stages Ⅰ and Ⅱ and BPD.There were no differences in stages Ⅰ and Ⅱ and the NC

No correlation could be found in the levels of NO and the histologic type of the tumors.The study of the correlation between NO and T-lymphocyte subpopulation in BWF showed that the levels of NO had negative correlation with in CD

4

/CD

8

ratio（r=-0.67

P

<

0.01）.In immunity study of LC

high levels of NO may be involved in the local immunosuppression.The determination of NO levels in BWF may be a helpful method for monitoring the immunity status and also useful for differential diagnosis of LC.