Abstract: Objective: To study the expressions of Cyclin D1 and p16 in the tissues of non-small-cell lung cancer(NSCLC) and its clinical significance.Methods: The expressions of Cyclin D1 and p16 in 62 cases of primary lung cancer were determined by immunohistochemical method and 20 cases of pulmonary benign cases acted as control.Results: The expressions of Cyclin D1 and p16 were high in the tissues of lung cancer,with a positive rate of 62.9% and 56.5%,respectively.The positive rates of Cyclin D1 and p16 in the 20 controls was 85.0%.The expression of Cyclin D1 was not related to the tumor's diameter,lymph node metastasis or clinical stages(P>0.05).The level of p16 was not related to the size of the tumor,but was associated with the lymph node metastases and clinical stages(P<0.005).Conclusions: Over expression of Cyclin D1 is related to the carcinogenesis and may act as a marker in the early diagnosis of lung cancer,but it has no correlation with the biological behavior or prognosis of lung cancer,while p16 is associated with the biological behavior and prognosis of lung cancer.