Novel estrogenic 17.alpha.-hydroxy-1,3,5(10),15-estratetraenes of the formula ##STR1## wherein R.sub.1 is H, lower alkyl or lower acyl, R.sub.2 is lower alkyl and R.sub.3 is H, lower alkyl, lower acyl or tetrahydropyranyloxy, are produced by (a) reacting a 16.alpha.,17.alpha.-epoxy-estratriene with lithium halide or HCl in glacial acetic acid; converting the resulting halohydrin into a 16-halo-17-tetrahydropyranyl ether; and splitting off hydrogen halide from therefrom; or (b) reacting the 16.alpha.,17.alpha.-epoxy-estratriene with diphenylselenide and alkali metal borohydride; oxidizing the thus-produced 17.alpha.-hydroxy-16.beta.-phenylselenide to the corresponding phenylselenide oxide; and forming the .DELTA..sup.15 double bond by heating with removal of phenyl--Se--OH.