In this study, we tried to investigate whether platycodin D significantly affects MUC5AC mucin production and gene expression induced by epidermal growth factor (EGF), phorbol ester (PMA) and tumor necrosis factor-$alpha$ (TNF-$alpha$) from human airway epithelial cells. Confluent NCI-H292 cells were pretreated with varying concentrations of platycodin D for 30 min and then stimulated with EGF, PMA and TNF-$alpha$ for 24h, respectively. MUC5AC mucin gene expression and mucin protein production were measured by RT-PCR and ELISA. The results were as follows: (1) Platycodin D was found to inhibit the production of MUC5AC mucin protein induced by EGF, PMA, and TNF-$alpha$, respectively. (2) It also inhibited the expression of MUC5AC mucin gene induced by the same inducers. These results suggest that platycodin D can regulate mucin gene expression and production of mucin protein, by directly acting on human airway epithelial cells.