The effect of glucocorticoids on respiratory glycoconjugate (RGC) secretion was studied in a cat tracheal organ culture system. Dexamethasone (10(-5) to 10(-9) M) added to culture medium for 24 h caused a dose-related reversible inhibition of RCG of as much as 40% with a peak effect at 24 to 60 h after initiation of dexamethasone treatment. A monoclonal antilipocortin antibody added to the cultures blocked the inhibitory effect of dexamethasone on RGC secretion and accelerated the reversal of the dexamethasone effect after discontinuation of dexamethasone treatment. A control antibody without antilipocortin activity had no effect on RGC secretion or dexamethasone-induced inhibition of RGC secretion. Measurement of the concentration of lipocortin in airways revealed a 220% increase after treatment with dexamethasone for 24 h. We conclude that dexamethasone inhibits RGC secretion through the induction of lipocortin synthesis.