Objective To study the relationship between endothel in-1 in plasma and TCD in patients with brain injury.Methods We measured dynamically the level of ET-1 in plasma on 33 adult brain injured patients. Cerebral vasospasm was detected by transcranal Doppler sonography (TCD).Results 1.During 6-8 days, 13-15 days after injury,there was a significantly positive correlation between the level of ET-1 in plasma and cerebral vasospasm (r=0.533,P=0.002;r=0.423,P=0.02),especially during 6-8 days after injury. The increase of the level of ET-1 in plasma paralleled paroled with the time of cerebral vasospasm developed. 2.During 6-8 days after injury, the level of ET-1 in plasma of patients with cerebral vasospasm was obviously higher than those without cerebral vasospasm obviously (P