D 4 : 5-Unsaturated-3-ketones of the cyclopentano-polyhydrophenanthrene series are ob-tained by subjecting a compound of this series having either no side chain in the 17-position or a side chain with no more than two carbon atoms and containing in rings A and B one of the groupings <FORM:0497394/IV/1> <FORM:0497394/IV/2> <FORM:0497394/IV/3> <FORM:0497394/IV/4> <FORM:0497394/IV/5> where X represents either a free or an esterified hydroxyl group, to the action of an agent or conditions capable of splitting off water or acid respectively. Agents mentioned for the splitting off of water include mineral acids in solution in organic solvents such as alcohol or dioxane, phosphorus oxychloride, bisulphates, formic or oxalic acid, acid anhydrides such as acetic anhydride or phosphorus pentoxide, catalysts such as iodine, or by the action of a raised temperature in an indifferent gas or under diminished pressure. The elimination of carboxylic ester residues is advantageously carried out by the action of heat in a vacuum. Compounds which are used as parent materials for the process of the present invention include the male and female sexual hormones, the corpus luteum hormone, and the suprarenal cortical hormone, that is to say, derivatives of aetio-cholane, hexahydro-oestrone, and pregnane. Compounds mentioned as suitable for use in this connection include D 5 : 6-androstentriols - (3 : 4 : 17), D 4 : 5 - androstentriols-(3 : 6 : 17), D 5 : 6 - 3 : 4 - dioxy - androstenones-17, D 4 : 5 - 3 : 6 - dioxy - androstenones - 17, 4-, 5- or 6-oxy-androstandiones-(3 : 17), 4-, 5-or 6 - oxy - androstanol - 17 - ones - 3, 3 : 5 : 6-trioxy-androstanones-17, 3 : 5 : 6 : 17-tetroxyandrostanes and their sterioisomerides. In addition, compounds which correspond in respect of ring A and B with those named but have at the carbon atom 17- of ring D the groupings in which the first carbon atom is the carbon atom -17: <FORM:0497394/IV/6> ; <FORM:0497394/IV/7> ; <FORM:0497394/IV/8> ; <FORM:0497394/IV/9> ; <FORM:0497394/IV/100> ; <FORM:0497394/IV/111> ; and <FORM:0497394/IV/122> Examples of such compounds mentioned are D 5 : 6-3 : 4 : 17 : 20 : 21-pentoxy-pregnenes, D 4 : 5-3 : 6 : 17 : 20 : 21-pentoxy-pregnenes, D 5 : 6-3 : 4 : 11 : 17 : 20 : 21-hexoxy-pregnenes, 3 : 5 : 6 : 17 : 20 : 21-hexoxy-pregnanes, 3 : 5 : 6-trioxy-pregnanones-(20). The group X may in the case where it is an esterified hydroxyl group be a benzoic, palmitic, acetic or a xanthic ester. In addition to the splitting off of water or acid in rings A and B, analogous reactions may take place at other parts of the molecule, for instance, groups at the position -17 may be eliminated. In the case where the side chain <FORM:0497394/IV/133> is present, one obtains ketols of the formula <FORM:0497394/IV/144> The sources of some of the parent materials for the present invention are indicated. Thus the unsaturated 4- and 6-oxy-compounds are made by the action of selenium dioxide on D 5 : 6- or D 4 : 5-3-oxy compounds, which may have carbonyl groups in the side chains. Some are also obtained from 3-oxy-5 : 6-dihalogen compounds by splitting off halogen halide. Others are prepared by the addition of pairs of hydroxyl groups to D 4 : 5-or D 5 : 6-unsaturated compounds. In the latter case, hydroxy groups are frequently added to any double links present in the side chain. 3-Keto compounds suitable for use according to the present invention may be obtained, for example, by the following processes: (1) D 4 : 5-androstendione-3 : 17 is converted into the 4-bromo-derivative by hydrogen bromide and then treated with dilute ammonia to yield 4 - oxy - androstandione - (3 : 17); (2) D 5 : 6-androstendiol-(3 : 17) gives with perbenzoic acid 5 : 6 - oxido - androstandiol - (3 : 17) which on reduction in presence of a nickel catalyst gives 3 : 5 : 17-trioxyandrostane and this on treatment with chromic acid gives 5-oxyandrostandione - (3 : 17); (3) D 5 : 6 - 3 - oxyandrostanone-17 is converted into the 6-bromo compound with hydrogen bromide which by treatment with sodium acetate gives the 3-oxy-6 acetoxyandrostanone-(17) and this on treatment with chromic acid gives 6-acetoxyandrostandione-(3 : 17). In examples of the process of the present invention: (1) D 5 : 6-androstentriol-(3 : 4 : 17) is boiled in alcoholic solution with hydrochloric acid, diluted with water and extracted with ether to give D 4 : 5-androstenol-17-one-3. The same compound is obtained in a similar manner from D 4 : 5-androstentriol-(3 : 6 : 17), or by heating 3 : 5 : 6 : 17-tetroxyandrostane with potassium bisulphate in a vacuum. (2) The mixture of D 5 : 6-3 : 4-dioxyandrostenone-17 and D 4 : 5-3 : 6-dioxy-androstenone-17 which is obtained by the action of selenium dioxide on dehydroandrosterone is treated in alcohol solution with sulphuric acid and worked up as in example (1) to give D 4 : 5-androstendione-(3 : 17). (3) The benzoate obtained from 4-oxy pregnandione-(3 : 20) by the action of benzoyl chloride in pyridine is heated in a high vacuum until almost the whole of the substance has sublimed. Benzoic acid is removed from the sublimate by washing with a bicarbonate and from the residue there is isolated by means of its semicarbazone the D 4 : 5 - pregnendione - (3 : 20). This compound may be obtained in a similar manner from 6-benzoxy-pregnandione-(3 : 20) as well as from 3 : 5 : 6-trioxy-pregnanone-(20) by dehydration with potassium bisulphate. (4) The mixture of D 5 : 6-3 : 4 : 17 : 20 : 21 pentoxy-pregnenes and D 4 : 5-3 : 6 : 17 : 20 : 21 pentoxy-pregnenes obtained by the action of selenium dioxide on D 5 : 6-3 : 17-dioxy-21-oxo-pregnene and subsequent reduction is treated in alcoholic solution with concentrated hydrochloric acid and worked up as in example (1) to give D 4 : 5-21-oxypregnendione-(3 : 20). Specifications 486,596 and 486,854 are referred to.