During the last two decades, a group of homeobox-containing genes, the HOX gene family, has been studied both in the context of embryonic development and neoplasia. In particular, there is accumulating evidence of the involvement of HOX abnormalities in a variety of malignancies, including breast cancer. However, little is known about the association of HOX genes with endometrial cancer, which is the most common malignancy of the female genital tract and is thought to be dependent on estrogen, like breast cancer. In this study, we detected overexpression of the HOXB13 gene in endometrial cancer cells and tissues from patients by quantitative real-time RT-PCR. To investigate whether overexpression of HOXB13 is involved in invasion or metastasis of endometrial cancer, we transfected antisense HOXB13/pcDNA3.1+ plasmid vector into endometrial cancer AN3CA cells by electroporation and performed in vitro chemoinvasion assay. We revealed that the invasive ability of antisense-transfectants showed a 90% reduction compared with parental cells and control transfectants (p<0.01). In addition, administration of 17beta-estradiol induced time- and dose-dependent responses of the HOXB13 expression in endometrial cancer AN3CA cells. These results suggest that overexpression of HOXB13 in endometrial cancer may be associated with the invasive ability of cancer cells with regulation by estrogen.