The results about effects of Maecmoondongtang on the pulmonary function of $SO_2$ exposed rats were summerized as follows: 1. Maecmoondongtang reavealed significant effect on decrease of the lung weight in pulmomary edema of rats. 2. Maecmoondongtang reavealed very significant effect on decrease of the TBA value of lung. 3. It was recognized Maecmoondongtang had signiftcant effect on decrease of glycoprotein contents in trachea. 4. It was recognized maecmoondongtang had significant effect on decrease of mucos area in tracheal epithelium. 5. Maecmoondongtang had effects on recovery of the cillia cells of tracheal epithelium and inhibition of mucous secretion. According to the above result. it was recognized Gamimaecdongtang had significant effect on decrease of lung weight in pulmonary edema. the TBA value. glycoprotein contents in trachea. and mucous area in tracheal epithelium. and recovery of the cillia cells of tracheal epithelium. and inhibition of mucous secretion. So I think we can take advantage of this medicine very usefully for treatment of pulmonary edema. pheumonia. acute and chronic bronchitis etc.