The aim of this study was to observe the expression of tissue factor (TF) of astrocytes in basic culture medium and under the condition stimulated by thrombin and to explore the relevant signal transduction pathways. The results showed that 4-bromo calcium ionophore (A23187) and phorbol 12-myristate 13-acetate (PMA) enhanced significantly the TF expression of astrocytes, but the expression was decreased markedly by trifluoperazine (TFP) and 1-(5-isoquinolinyl sulfonyl)-3-methyl-piperazine (H7) in the basic medium. Thrombin increased significantly the TF expression of astrocytes, which was obviously inhibited by TFP and H7. The results above indicate that astrocytes can express TF activity in the basic medium, which is promoted by thrombin, probably through some pathways involving Ca2+/CaM and protein kinase C (PKC).