Present test observated the synthesis and expression of endothelin(ET) and nitric oxide synthetase(NOS) in rabbit' s atherosclerotic plaque(AP) on polypeptide and gene transfer.Histochemistry and immunohistochemistry shown that in proliferating vascular smooth muscle cell (VSMC) within AP, synthesis of ET was increased while that of NOS was significantly decreased;Meanwhile, in situ hybridization also shown that the transfer of ET mRNA was great increased while that of NOS mRNA was great decreased within 5 cases and only within 1 case,a little of NOS mRNA was expressed and the range was limited.So we believed that in aortic VSMC, un-balence of between ET and NOS may be involved in the occurrence and development of AP.