In order to find the relationship between endothelin and asthma, we investigated the level of plasma endothelin of guinea pigs with asthma, and the bronchoconstriction of endothelin to the guinea pigs. We also measured the plasma concentration of PGE2 TXB2 PGF2 alpha LTC4 after using ET intravenously. The results showed that the level of plasma endothelin elevated significantly in guinea pigs with asthma. The bronchoconstriction was positively related to the dosage of endothelin intravenously. PLA2 antagonist and cyclooxygenase inhibitor can reduce the bronchoconstriction caused by endothelin. All these indicated that endothelin may contribute to the cause of asthma.