On the model of endodenudation of the rats' thoracic aortae, the interaction of endotheliurn regrowth and intimal hyperplasis with release of endothelin was studied. The results indicated that endothelin was detected in the incubating media of rats' vessels with or without endotholium after procedure, but not in those without endotheiium in sham control. In preparations with endothelium or those without it, thrombin (4u/ml) stimulated the release of the peptide after endodenudation. Thus, we concluded that the increase of non—endothelium derired endothelin release is the major course of increased endothelin release after ballooning of rats' thoracic aortae.