Aim This study is to investigate the changes ofconstitutive nitric oxide synthetase(cNOS )gene and endothelin -1(ET-1)gene expression after endothelial injury.Methods Endothelial cells of rats'thoracic aortaewere injuried by Fogarty balloon catheter. Thoracic.aortae tissues were under histological examination at 1,5,15 and 20 days after endothelial injury.The cNOS gene and ET-1 gene mRNA expressions in thoracic aortae tissues at different time stage were determined by reverse transcription polymerase chain reaction(RT-PCR)methods.Results Histological examination showed smooth muscle cell(SMC)proliferation and intimal thickening in thoracic aortae at 5,15 and 20 days after endothelialinjury.Some sites of intima began to reendothelialize at 20 days.The ET-1 gene expression in thoracic aortae tissue increased significantly at l and 5 days,and s still maintained at higher level at 15 and 20 days than control.To the opposite,the cNOS gene expression disappeared at 1 day,and was lower than control at 20 days.Conclusion The results indicated that alterations of ET-1 gene and cNOS gene expression were associated with SMC proliferation in this endothelial injury model.