We conducted this study to investigate whether baicalin, baicalein or schizandrin significantly affect MUC5AC mucin production induced by epidermal growth factor (EGF) or phorbol ester (PMA) in human airway epithelial cells. Confluent NCI-H292 cells were pretreated with varying concentrations of baicalin, baicalein or schizandrin for 30 min and then stimulated with EGF or PMA for 24 h, respectively. MUC5AC mucin protein production was measured by ELISA. The results were as follows: (1) Baicalin was found to inhibit the production of MUC5AC mucin protein induced by both EGF and PMA. (2) Baicalein, the aglycone of baicalin, also inhibited MUC5AC mucin production. (3) Schizandrin, derived from Schizandrae Fructus, inhibited MUC5AC mucin production by the same inducers. These results suggest that baicalin, baicalein and schizandrin can regulate the production of mucin protein by directly acting on human airway epithelial cells.