Abstract: Objective: To study the effects and clinical significance of plasmal thromboxane B_2 (TXB_2), platelet alpha granule membrance protein-140 (GMP-140), 6-Keto-PGF1a (6-K- PGF1α), endothelins(ET), tissue type plasminogen activator(tPA)and plasmingen activator inhibitor-1 PAI-1) in patients with cerebral arteriosclerosis and cerebral thrombosis. Methods: Plasma TXB_2, GMP 140, 6-K-PGF1 α and ET levels were determined by radioimmunoassay. Plasma tPA and PAI were determined by the chromogenic peptide substrate method in controls and in patients with cerebral arteriosclerisis and cerebral thrombosis. Results: ①The levels of plasma TXB_2 and GMP-140 were significantly higher in patients with cerebral arteriosclerisis and cerebral thrombosis than in the control group(P0.01). ② The level of 6-K-PGF1α was higher and the level of ET was lower in patients with cerebral thrombosis than in the controls(P0.01), while in the levels of 6-K-PGF1α and ET but no difference was found in patients with cerebral arteriosclerisis compared with controls(P0.05). ③ The levels of tPA and tPA/PAI were significantly lower in patients with cerebral arteriosclerise and cerebral thrombosis than in controls. Although the PAl level increased in patients with cerebral arteriosclerise and cerebral thrombosis, no difference was found in statistics. Conclusion: Activation of platelets, injury of endothelial cell and decreased activity of fibrinolysis in patients with cerebrovascular disease may be involved in the development of these diseases. Appropriate treatment should be adopted targettd on the above abnorrnality.