This paper aims to elucidate the changes and pathophysiologic roles of endothelin (ET) in trauma patients with hemorrhagic shock. The plasma levels of ET were measured by radioimmunoassay in 32trauma patients with hemorrhagic shock (Experimental Group) and 37 normal control subjects (Normal Control Group, Group A). The trauma patients were divided into three groups: Group B as the severe injuries of single anatomic area of AIS-90, Group C, D as the multiple injuries with ISS < 16, ISS ≥ 16 respectively. According to the volume of blood loss, the patients were also divided into three groups: <1 500ml, 1 500-3 000ml, > 3 000ml. Plasma ET concentrations were significantly higher in trauma patients than those in normal subjects (P<0.001). The level of ET increased significantly in Group D as compared with Group B and C (P<0.05, 0.001 respectively). No significant difference in ET levels existed among three groups of blood loss (P>0.05). The concentrations of plasma ET were decreased gradually following injury, however, there was no significant difference among the time intervals. The plasma levels of ET could be a significant index for judging the severity of injury. Elevation of plasma ET might play an important role in maintaining systemic blood pressure, tissue perfusion of vital organs and enhancing hemostasis of trauma loci in the early stage of injury and shock. Prolonged elevation of plasma ET might be a precursor of unfavourable prognosis.