To evaluate the effect of dexamethasone on the expression of aquaporin-1 (AQP-1) in cultured bovine trabecular meshwork cells, bovine trabecular meshwork cells were cultured in vitro and reproduced to the third and the fourth generation, then treated with dexamethasone at the concentrations of 5, 25, 50, 250 μg/L respectively for 7 days. Immunohistochemical technique-supervision method was employed to measure, and image analysis system to analyze the expression of AQP-1 in normal cultured bovine trabecular meshwork cells and those treated with dexamethasone. In normal bovine trabecular meshwork cells, the grayscale of AQP-1 positive staining was 167.94±1.18, while it was 168.92±0.91, 176.72±1.80, 180.64±1.31, 185.64±1.58 in cells treated with 5, 25, 50, 250 μg/L concentrations of dexamethasone. When the concentration of dexamethasone was higher than 25 μg/L, the expression of AQP-1 was significantly inhibited (P<0.05). The regulation of AQP-1 expression by dexamethasone in cultured bovine trabecular meshwork cells in vitro may be one of causes that retard the aqueous outflow in glucocorticoid- induced glaucoma.