This study was carried out to investigate the effects of Gooboeum extract on the inhibitory contractile action of acetylcholine in the control and sensitized rat. The results were obtained as follows: 1. The acetylcholine contractile force of the trachea smooth muscle with epithelium was significantly relaxed by Gooboeum. 2. Dose-response of acetylcholine from the trachea smooth muscle pretreated Gooboeum was not changed. 3. Effect of Gooboeum on the inhibitory contractile action of trachea smooth muscle pretreated propranolol was not significantly inhibited. 4. The inhibitory contractile action of acetylcholine of trachea smooth muscle pretreated indomethacin was not significantly changed by Gooboeum. 5. Effects of Gooboeum extract on the inhibitory contractile action of acetylcholine of trachea smooth muscle pretreated methylene blue was not significant. 6. The contractile force of acetylcholine of the trachea smooth muscle without epithelium was significantly inhibited by Gooboeum. 7. Dose-response of acetylcholine of the trachea smooth muscle pretreated Gooboeum was not significant. 8. Effects of Gooboeum extract on the inhibitory contractile action of acetylcholine of the trachea smooth muscle pretreated propranolol was significantly inhibited. 9. Effects of Gooboeum extract on the inhibitory contractile action of acetylcholine of the trachea smooth muscle pretreated indomethacin decreased. 10. Effects of Gooboeum extract on the inhibitory contractile action of acetylcholine of the trachea smooth muscle pretreated methylene blue was not significant.