Abstract: AIM: To evaluate the effects of caffeic acid and ferulic acid on the biological responses induced by endothelin -1(ET-1) and study the mechanism of their antagonistic actions on endothelin-1. METHODS: Acute death of mouse induced by iv ET-1, isolated artery ring constrictions and rabbit aortic vascular smooth cells (RAVSMC) proliferation induced by ET-1 were used to observe the antagonistic effects of caffeic acid and ferulic acid on ET-1. Also, the ¹²⁵I-ET-1 binding with 3T3 cells were employed to measure the effects of caffeic acid and ferulic acid on binding potency. RESULTS: Caffeic acid and ferulic acid were shown to increase the mouse survival time induced by ET-1 iv administration and decrease the vasoconstrictions of isolated aortic rings. Both acids were found to bind competitively with ¹²⁵I-ET-1 on 3T3 cells. CONCLUSION: Caffeic acid and ferulic acid are a new kind of non peptide endothelin antagonists.