Abstract: Objective: To study the effect of full-length cyclin B1 antisense cDNA(AS-CLB1) on Taxotere in inhibiting prolifer-ation of Lewis lung carcinoma cells (LL/2) in vitro and in vivo and to provide the foundation for the feasibility of treating human lung cancer and other malignancies with AS-CLB1 combined with Taxotere. Methods: LL/2 parent cells, LL/2/ vector and LL/2/AS-CLB1 transfectants(LP, LV and LA cells) were treated with Taxotere(0.01 nmol/L~0.1 μ mol/L) in vit-ro. The cytotoxicity of Taxotere was evaluated by MTT assay at 1h and 24h after treatment. After inoculation of the three types of cells, C57BL/6 mice were treated with Taxotere (15 mg/kg/day) once every three days for four cycles. Cell cycle and apoptosis in the tumor tissues were determined by flow cytometry. Results: The survival rate of LA cells treated with taxotere was lower than that of the controls (LP and LV cells; P<0.05). At 1h after treatment with taxotere (80nmol/L), the survival rate was (4.56± 1.21)% in LA cells, (46.26± 3.53)% in LP cells and (44.25± 2.21)% in LV cells. At 24h after treat-ment with 20nmol/L Taxotere, the survival rate was (5.21± 1.39)% in LA cells, whereas it was (36.17± 3.63)% in LP and (35.15±3.63)% in LV cells. The tumor volume in the LA group was also lower than that of the controls(LP and LV group;P<0.05). At 30 days after the inoculation of tumor cells, the tumor volume was 421.68± 30.16mm³ in the LA group,1981.29± 318.56mm³ in the LP group and 1673.36± 297.96mm³ in the LV group. Compared with the control groups, the cells in tumor tissues of the LA group showed G 1 arrest and increased apoptosis(P<0.05). There were (89.7± 0.5)% cells in G 1 phase and the apoptotic ratio was (79.5± 1.2)% in the LA group. Moreover, 70% of the mice in the LA group were still alive at the end of the observation period for the survival studies. In contrast, only 30% of the mice in the LP group and 40% of the mice in the LV group were still alive. The survival rate in the LA group was significantly higher than in the control groups (P<0.01). Conclusion: AS-CLB1 can increase the inhibitory effect of Taxotere on the proliferation of LL/2 cells in vitro and in vivo. It enhances the anti-tumor activity of Taxotere by inducing cell apoptosis and G 1 arrest.