Abstract: Objective: To investigate whether neoadjuvant chemotherapy can induce tumor cell apoptosis in non- small cell lung cancer patients, and to study its effect on cell proliferation. Methods:Fifty- six patients with stage III non- small cell lung cancer were treated with neoadjuvant chemotherapy, and 50 with the same stage were directly treated with surgery as control. Apoptosis index (AI) of tumor cells was assayed by TdT- mediated dUTP nick end labeling (TUNEL) and Cell proliferation antigen (ki- 67) was examined using immunohistochemical labeled streptavidin biotin (LSAB) in the cancer samples. Results: Tumor cell AI in neoadjuvant group (X=9.34%) was significantly higher compared to control group (X=5.27%) (P<0.01). Ki- 67 positive expression rate in neoajuvant group (X=35.68%) was significantly lower than that in control group (X=59.35%) (P<0.01). There was a significant negative association between AI and Ki- 67 in both neoadjuvant chemotherapy group and control group (P<0.01).Conclutions: Neoadjuvant chemotherapy can induce tumor cell apoptosis and can inhibit the tumor cell proliferation in non- small cell lung cancer.