Various steroids, including glucocorticoids, were observed to exert a direct effect on the rates of translation of several myelin-protein specific transcripts in a cell-free, reticulocyte lysate system. Hydrocortisone caused a twofold stimulation in the translation of mRNAs of myelin basic protein and proteolipid protein. It inhibited the translation of 2',3'-cyclic nucleotide 3'-phosphodiesterase mRNA by 50%, and had no effect on the translation of a number of other mRNAs. The data suggest that steroid-mediated translational regulation may serve as a novel mechanism to modulate the expression of myelin protein genes at the translational level.