This study examined the expression of the anterior gradient-2 (AGR2) protein and Muc5ac protein in the lung tissues of asthmatic mice and the effect of dexamethasone, with an attempt to explore the role of AGR2 in the over-secretion of mucus in the airway. Eighteen BALB/c mice were divided into asthma group, control group and dexamethasone group. In dexamethasone group, dexamethasone was intraperitoneally administered. Expression of AGR2 protein and Muc5ac protein in the murine lung tissues was immunohistochemically detected. IL-13 level was determined in the bronchoalveolar lavage fluid (BALF) by ELISA. The results exhibited that the expression of AGR2 protein in asthma group (0.522 +/- 0.041) was significantly higher than that in normal controls (0.361 +/- 0.047) (P < 0.01) and bore a positive linear relationship to the expression of Muc5ac protein (r=0.873, P < 0.05) and IL-13 level (r=0.828, P < 0.05). Expression of AGR2 protein in the dexamethasone group (0.456 +/- 0.049) was significantly lower than that in the asthma group. It was concluded that: (1) the expression of AGR2 protein was significantly higher in asthmatic mice as compared with their normal counterparts; (2) the expression was obviously related to the expression of Muc5ac protein and IL-13; (3) dexamethasone could down-regulate the expression of AGR2 protein. Our findings suggested that AGR2 might be involved in the over-secretion of mucus in the airway in asthma.