Pathogenic factors associated with COPD such as cigarette smoke, pro-inflammatory cytokines and bacterial infections can individually induce respiratory mucins in vitro and in vivo. Since, co-presence of these factors is common in lungs of COPD patients, we hypothesized that cigarette smoke can amplify mucin induction by bacterial exoproducts and pro-inflammatory cytokines, resulting in mucin hyperproduction. We demonstrated that cigarette smoke extract (CSE) synergistically increased gene expression and protein production of MUC5AC mucin induced by LPS or TNF- in human airway epithelial NCI-H292 cells. CSE also enhanced expression and production of MUC5AC mucin induced by epidermal growth factor receptor (EGFR) ligands TGF- and amphiregulin, as well as LPS- and TNF--induced expression and/or release of TGF- and AR. Furthermore, BPDQ, a potent inhibitor of EGFR blocked synergistic induction of MUC5AC mucin. H₂O₂ mimicked the synergistic effects of CSE, while antioxidant N-acetyl-L-cysteine prevented synergistic induction of MUC5AC mucin by CSE. In a rat model of LPS-induced airway inflammation, concurrent cigarette smoke inhalation enhanced mucin content of the bronchoalveolar lavage fluid, muc5AC gene expression and mucous-cell metaplasia in the airways. These results suggest that cigarette smoke has the potential to synergistically amplify induction of respiratory mucins by pro-inflammatory stimuli relevant to COPD pathogenesis and contribute to mucin hyperproduction observed in COPD patients.