Tenascin is an extracellular matrix glycoprotein which plays a role in cell attachment, proliferation and migration. To elucidate the function of tenascin in the proliferation of endometrial carcinoma, we studied tenascin expression in the endometrial carcinoma of 36 cases. In 22 of the carcinomas, tenascin expression was intense in the entire extracellular space, especially at the front of muscle invasion. Furthermore, in cases with metastases, deep invasion into muscles and vascular invasion, the rate of tenascin expression was significantly high. Immunoelectron microscopy revealed the tenascin reaction product in the stroma around fibroblasts located some distance from the basal lamina of cancer cells. On the other hand, tenascin expression was found in a high proportion of cases showing weak or no expression of estrogen receptor, and intense expression of transforming growth factor-beta 1. These results suggest that tenascin not only promotes cell proliferation and invasion but also inhibits further proliferation of carcinoma.