Tumor progression is often regulated through interactions between carcinoma cells and host stromal cells. In this study of endometrial cancer, we investigated one mechanism potentially involved in hepatocyte growth factor (HGF)-mediated cancer-stromal interactions. Endometrial cancer cells (HEC-1 and ISHIKAWA) expressed the c-met receptor, but HGF did not. HGF, however, did stimulate the proliferation and invasion of these cells. The HGF gene was expressed in stromal cells, which had been separated from primary cultures of endometrial cancers, 6.4 times more than in isolated normal endometrial stromal cells. Immunohistochemical staining revealed immunoreactive HGF in cancer stromal cells, the staining intensity being more pronounced in cancer tissue than in normal endometrium. The conditioned medium from normal epithelial cells and cancer cell lines induced HGF production in normal stromal cells. We identified basic fibroblast growth factor as an HGF inducer derived from endometrial cancer cell lines. Basic fibroblast growth factor derived from tumor cells may induce HGF in endometrial stromal cells, whereas stromal cell-derived HGF leads to the invasive growth of carcinoma cells. These interactions, mediated by HGF and HGF inducers, may play a significant role in the progression of endometrial cancer.