Objective To discuss the dynamic changing characteristics of plasma endothelin in Tibetan neonates of plateau area with hypoxic - ischemic encephalopathy. Methods Plasma ET level has been determined for 10 days 72 hours after birth by radioimmunoassay in 70 tibetan neonates with HIE.The control group consisted of 20 healthy neonates. Results During acute stage, plasma ET levels of mild, moderate and severe groups were significantly higher that of control group (P ＜ 0.001 ). During acute stage, plasma ET level was closely related with the severity of HIE. Severer HIE was, higher ET level. Conclusion ET was involved in the regulation of HIE.