In this paper, the authors present the synthesis of the 21-acetate pregna-4,9(1l)-diene-17alpha,21-diol-3,20-dione from 9alpha-hydroxy androstenedione, an important intermediate for synthesis of corticoids such as hydrocortisone and prednisolone. The structure of the product and its intermediates was examined by physical methods such as: IR, MS, IH and 13C NMR.