Tissue factor (TF) is a cell surface glycoprotein that initiates the extrinsic coagulation protease cascade and it is expressed in some tumor cells. TF belongs to the interferon receptor family, and it is one of the early immediate genes, suggesting that TF has a biological function other than hemostasis. We investigated the expression of TF in gliomas. Immunocytochemistry showed the expression of TF in 3 glioma cell lines. Immunohistochemical analysis of 44 surgical specimens revealed that all gliomas were positive for TF, and 19 (95%) of 20 glioblastomas, 12 (86%) of 14 anaplastic astrocytomas and 1 (10%) of 10 benign gliomas were moderately or strongly positive for TF. Our study showed that TF is expressed in gliomas, and that the level of TF expression is correlated with the grade of malignancy of the glioma, suggesting that TF may participate in cell growth.