Objectives : The author intended to investigate Seonbangpaedoktang (SBPT) significantly affect in vivo and in vitro mucin secretion from airway epithelial cells. Methods : In vivo experiment, the author induced hypersecretion of airway mucin, hyperplasia of tracheal goblet cells and the increase in intraepithelial mucosubstances. Effects of orally-administered SBPT during 1 week on in vivo mucin secretion and hyperplasia of tracheal goblet cells were assessed. For in vitro experiment, confluent hamster tracheal surface epithelial (HTSE) cells were metabolically radiolabeled and chased in the presence of SBPT to assess the effect of the agent on 3H-mucin secretion. Total elution profiles of control spent media and treatment sample through Sepharose CL-4B column were analysed. Possible cytotoxicity of the agent was assessed by measuring LDH release. Also, the effect of SBPT on contractility of isolated tracheal smooth muscle was investigated. Results : SBPT inhibited hypersecretion of in vivo mucin and inhibited the increase of number of goblet cells ; SBPT did not affect in vitro mucin secretion and the secretion of the other releasable glycoproteins with less molecular weight than mucin from cultured HTSE cells, without significant effect on LDH release; SBPT did not affect Ach-induced contraction of isolated tracheal smooth muscle. Conclusions : SBPT can inihibit hypersecretion of in vivo mucin and the author suggest that the effect SBPT with their components should investigate further.