Esophageal squamous cell carcinoma (ESCC) is a common and highly fatal cancer in Japan. Systemic chemotherapy is used, but some tumors show resistance to it. The mechanisms of tumor resistance to chemotherapy remain largely unknown. We determined the chemosensitivity of 15 ESCC cell lines (TE-1-5, TE-8-15, KYSE140 and KYSE150) to docetaxel by clonogenic and MTT assays. We used cDNA microarray analysis and quantitative RT-PCR to determine which genes might determine resistance to docetaxel. Small interfering RNA (siRNA) was used to suppress gene expression and its effect on the chemosensitivity of the cell was determined. The cell line with the most resistance to docetaxel was TE-2. Using microarray analysis, we identified beta1 integrin (ITGB1) to be overexpressed in this cell line. Higher expression of ITGB1 mRNA was significantly associated with docetaxel resistance (n=15, r2=0.66, P=0.0110). Suppression of ITGB1 expression using siRNA sensitized the TE-2 cells to docetaxel. These data suggest that overexpression of ITGB1 may be related to resistance to chemotherapy and that targeting ITGB1, particularly in patients on docetaxel therapy, may enhance the effect of chemotherapy in patients with ESCC.