Abstract: Objective:To observe the expression of inducible nitric oxide synthases(iNOS) in laryngocarcinoma tissues and its role in the invasion and metastasis of laryngeal carcinoma. Methods:The expression of iNOS in 66 cases of laryngealcarcinoma tissues and the normal mucous membrane were detecdted by immunohistochemistry S-P method. The correlation between the expression of iNOS and the clinical stage,clinical classification,pathological grade and lymph node metastasis of laryngeal carcinoma was analyzed. Results:The positive rate of iNOS in laryngealcarcinoma tissues and the normal mucous membrance was 81.82% and 6.06%,respectively(P<0.05); the expression of iNOS was significantly correlated with the clinical stage and classification of patients with laryngeal carcinoma (P<0.05),but had no relation with the patients'age,pathological grade or lymph node metastasis(P>0.05). Conclusions:iNOS may act as an important tumor marker in lymph node metastasis of laryngeal carcinoma. It plays an important role in the invasion,metastasis and prognosis of laryngeal carcinoma.