Abstract： Objective To screen sensitive drugs and guide clinical chemotherapy of lung cancer by using MTT drug sensitivity test in vitro. Methods One hundred cases of lung cancer registered to Department of Respiratory Diseases in our hospital between January 2008 and December 2009 were randomized into the MTT test group and the control group (n=50 each). The patients in MTT test group underwent MTT drug sensitivity test to guide chemotherapy. Those who tested drug- insensitive received empirical treatment, so were the patients in the control group. The clinical effects were observed and evaluated as related to drug sensitivity test in vitro. Results The drug sensitivity test yielded an overall rate of 80.0％ (32/40) matching curative effects, with the positive matching ratio being 81.3％ (26/32)and the negative matching ratio being 75.0％(6/8). The sensitivity and the specificity of MTT drug sensitivity test was 92.9％(26/28) and 50.0％ (6/12) respectively. The rate of response was 81.3％ (26/32)in patients with MTT drug sensitivity tost-guided chemotherapy and 60.0％ (30/50) in controls on empirical chemotherapy (P＜ 0.05). Conclusions There is a close association between MTT drug sensitivity test in vitro and clinical effects of chemotherapy, indicating MTT drug sensitivity test may provide guidance for chemotherapy and help improve clinical effects among patients with lung cancer.