Abstract: Objective:To study the role of extracellular regulated protein kinases (ERK-1/2) in vein grafts.Methods:Forty-five adult rabbits were randomly divided into control group,VG group and VG/UO group.Carotid artery bypasses were performed using reversed autologous external jugular vein.A segment of each sample was analyzed with western blot.Results:Intimal hyperplasia was observed 28 days after the operation in group VG.The reversed autologous external jugular vein grafts resulted in activation of ERK-1/2 with stronger activation occurring at 3 h and at 3 d.Proliferating cell nuclear antigen (PCNA) began to express 3 h after the operation and lasted for 28 d.The activation of ERK-1/2 in group VG/UO was significant inhibited after the application of UO126,and there was no peak of activation detected.Conclusions:ERK-1/2 activation may be the key point in the process of intimal hyperplasia.Inhibition of the ERK-1/2 pathway inhibits intimal hyperplasia,and therefore,results in inhibition of the late events.