a-Terpineol as an another antiasthmatic principle of essential oil of Artemisia argyi was studied. It had relaxant effect on isolated guinea pig tracheal smooth muscle preparations, the effective threshold concentrations being between 2. l-4.2x10-5 g/ml, and the EC50 being 0.71-1.15x10-4g/ml. It could protect guinea pigs from the acetylcholine and histamine-induced asthma when given orally or aer-osolly. The level of cAMP in the tracheal smooth muscle of guinea pigs was elevated in the presence of l0-4g/ml a- terpineol. The drug could block the development of desensitization to isoproterenol on isolated guinea pig tracheal smooth muscle preparations, and its relaxant effect did not be- influenced on the desensitized preparations also. In addition, a-terpineol had the Inhibitory effect of anaphylactic mediators release antagonistic effect of the mediators, antitussive and expectorant effect, and the inhibitory effect on isolated ed guinea pig atria. The toxiicological studies showed that it had good safety margin. ( + ) - a-Terpineol amd (-) a -terpineol had similarquality and potency of actions.