Abstract： Objective To observe the effects on cell proliferation,cell cycle distribution and apoptosis when sequentially administered gefitinib and docetaxel in different cell lines,and to evaluate the interaction of two drugs. Methods A431, A549, SPC-A1 and NCI-H292 cells were treated with gefitinib and docetaxel concurrently or sequentially. The anti-tumor effects were measured by growth inhibition by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-terazolium bromide assay. The cell cycle distribution and apoptosis of A549 and A431 cell lines were measured by flow cytometry. Results The combination of gefitinib and docetaxel had different effects in different cell lines which depended on the sequence. When cells were exposed to docetaxel followed by gefitinib, the cell survival percentage decreased in all cell lines. When gefitinib was given before or concurrently with docetaxel, the cell survival percentage decreased in A431 lines,which showed a synergistic effect between two drugs. Meanwhile,it increased in A549, NCI-H292 and SPC-A1 cell lines, which showed an antagonistic effect. The synergistic or antagonistic effect could be weakened by a sufficient interval between two drugs. The measurements by flow cytometry showed the apoptosis percentage in A549 and A431 cell lines were significantly different. Conclusions The combination of gefitinib and docetaxel has different effects in different cell lines which depend on the sequence. The mechanism worths further research.