Objectives: In this study, the author investigated whether Haengso-tang (HST) and Chwiyeon-tang (CHT) affect both in vitro mucin secretion and MUC5AC gene expression in airway epithelial cells and in vivo mucin secretion from animal model for airway mucus hypersecretion. Materials and Methods: Confluent HTSE cells (non-labeled) were chased for 30 min in the presence of HST and CHT to assess the effects of the agents on mucin secretion by enzyme-linked immunosorbent assay (ELISA), with removal of oriental herbal medicine extract from each agent-treated sample by centrifuge microfilter. Also, the effects of the agents on TNF- or EGF-induced MUC5AC gene expression in human airway epithelial cells (NCI-H292) were investigated. The author also induced hypersecretion of airway mucus by exposure of rats to SO2 for 3 weeks. Effects of orally-administered HST and CHT during 1 week on in vivo mucin secretion from tracheal goblet cells of rats were assessed using ELISA. Results: (1) HST significantly decreased in vitro mucin secretion from cultured HTSE cells. However, CHT did not affect in vitro mucin secretion from HTSE cells; (2) CHT significantly inhibited the expression levels of EGF- or TNF-alpha-induced MUC5AC gene in NCI-H292 cells. However, HST did not affect the expression levels of EGF- or TNF-alpha-induced MUC5AC gene in NCI-H292 cells; (3) CHT significantly inhibited hypersecretion of in vivo mucin. However, HST did not affect hypersecretion of in vivo mucin. Conclusion: These results suggest that CHT can not only affect the secretion of mucin but also the expression of the mucin gene and could be helpful for treating pulmonary disease caused by secretion of mucin.