Objective To study the effect of tumor necrosis factor(TNF) and endothelin(ET) on the formation of murine hyperdynamic circulatory syndrome(HCS).Methods Circulation stable HCS model was produced in rats by partial portal vein ligation.Portal blood TNF and ET was determined pre and post injection of anti rat TNF and hemodynamics was monitored simultaneously.Results TNF level did not change 0 5 hour after partial portal vein ligation,but it increased significantly at 24 hour and maintained at this high level thereafter. ET was on a small increment at different time after partial portal vein ligation.The TNF level decreased significantly to the level in controls and ET remained unchanged after injection of anti rat TNF,while HCS was partially ameliorated. Conclusion [WT5”BZ] TNF may be related with the start and maintenance of HCS,and there is no causality between ET and the development of HCS.