These studies were carried out to investigate the effect of Insameumja water extract on the inhibitory contractile action of acetylcholine in guinea pig. The results of these studies were as follows; 1. Contractile force of acetylcholine from trachea smooth muscle in guinea pig was significantly inhibited by Insameumja. 2. Dose-response of acetylcholine pretreated Insameumja in guinea pig was not significantly changed. 3. Inhibitory contractile action of acetylcholine pretreated propranolol in guinea pig was decreased. 4. Inhibitory contractile action of acetylcholine pretreated indomethacin was significantly changed by Insameumja. 5. Inhibitory contractile action of acetylcholine pretreated methylene blue was not significantly changed by Insameumja.