Long-term memory formation for a passive avoidance task in day-old chicks, which requires a late phase of glycoprotein fucosylation (5-8 hr posttraining), is dependent on a corticosterone action in the brain. In addition, corticosterone enhances late-phase fucosylation. In this study, the authors explored (a) to what extent the memory-facilitating action of corticosterone is dependent on protein fucosylation and (b) whether a protein synthesis mechanism might be involved in the steroid effects on memory and late-phase fucosylation. A combination of psychopharmacological and biochemical experiments, including the fucosylation inhibitor 2-deoxygalactose (2-DG), the protein synthesis inhibitor anisomycin (ANI), and radiolabeled fucose, indicated that the late phase of glycoprotein synthesis involved in the memory-facilitating effect of corticosterone occurs on newly synthesized proteins.