Tissue factor (TF) is a cell-surface glycoprotein responsible for initiating the extrinsic pathway of coagulation; this is inhibited by tissue factor pathway inhibitor (TFPI). As TF reportedly regulates tumor growth and angiogenesis, we investigated the role of TF in meningioma. Using immunohistochemical methods, we studied the expression of TF, TFPI, MIB-1 labeling index in 44 meningiomas to determine whether those factors reflect histological grade and proliferative ability. CD31 and CD68 immunostaining was used to assess vascular density and macrophage infiltration, respectively. Additionally we assessed the influence of TF on meningioma cell proliferation by MTT assay. TF was expressed in 1 of 34 (2.9%) benign, 1 of 5 (20%) atypical, and all of 5 anaplastic meningiomas. TFPI was detected in 2 benign (5.9%), 1 atypical (20%), and 3 (60%) anaplastic meningiomas. Both TF and TFPI expression was significantly correlated with the MIB-1 labeling index (LI). However, neither TF nor TFPI showed a correlation with vascular density. The density of tumor-associated macrophages was not correlated with TF or TFPI immunoreactivity. MTT assay revealed that TF increased the proliferation of meningioma cells. Although some macrophages expressed TF, a great number of the TF immunopositive parenchymal cells in the meningiomas were tumor cells. The present study suggest that the TF system reflects the proliferative ability and malignancy of meningiomas.