Close to birth rat fetuses have lungs which are depleted in retinyl esters. Glucocorticoids administered to pregnant rats accelerate this process. We have investigated changes in fetal lung levels of retinol and retinyl palmitate and accompanying morphological changes after administration of dexamethasone to pregnant rats on day 18 of pregnancy. Here we show that this depletion temporarily coincides with prenatal morphological maturation of the lungs. The data presented support the idea that the maturational effect of glucocorticoids in the developing lungs is linked to vitamin A metabolism.