The invention comprises 10a -methyl-9a -steroids of the general formula I shown in the figure wherein R1 represents a hydrogen atom or a methyl group, R2 represents no double bonds or one or more double bonds at one or more of positions 1, 2, 3, 4, 5, 6, 15 and 16 in the steroid nucleus, R3 represents a hydrogen or halogen atom, or a methyl, ethyl, hydroxy, etherified hydroxy or esterified hydroxy group, R4 represents a keto, hydroxy, etherified hydroxy or esterified hydroxy group, R5 represents a hydrogen or halogen atom, R6 represents a hydrogen or halogen atom or a methyl, hydroxy, etherified hydroxy or esterified hydroxy group, R7 represents a hydrogen or halogen atom, R8 represents a hydrogen atom or a hydroxy or keto group, R9 represents a hydrogen atom or a saturated or unsaturated hydrocarbon group containing from 1 to 6 carbon atoms or such group in which one or more hydrogen atoms is or are replaced by one or more hydroxy, etherified hydroxy or esterified hydroxy groups, and/or double bonded oxygen atoms, R10 represents a hydrogen atom or a hydroxy, etherified hydroxy or esterified hydroxy group (R9 and R10 being <FORM:0929272/IV(a)/1> <FORM:0929272/IV(a)/2> <FORM:0929272/IV(a)/3> <FORM:0929272/IV(a)/4> <FORM:0929272/IV(a)/5> <FORM:0929272/IV(a)/6> <FORM:0929272/IV(a)/7> <FORM:0929272/IV(a)/8> <FORM:0929272/IV(a)/9> not both hydrogen) or R9 and R10 together represent a keto group, and R11 represents a hydrogen atom or a methyl, hydroxy, etherified hydroxy or esterified hydroxy group; and the preparation of 10a -methyl-9a -steroids of the general formula VII shown in the Figure wherein R4 represents a keto, hydroxy, etherified hydroxy or esterified hydroxy group and R2 represents no double bonds or one or more double bonds at one or more of positions 1, 3, 4, 5 and 6 by oxidising 10a -methyl-9a -steroids of the general formula VI shown in the Figure wherein QVI represents a methyl group, and QVII represents an aldehyde group or a cyanhydric or bisulphite addition group derived therefrom or an O-acyl group derived from an aliphatic carboxylic acid having from 1 to 6 carbon atoms or an aromatic carboxylic acid, or QVI represents hydrogen and QVII represents a -COOR group wherein R represents an alkyl group having from 1 to 6 carbon atoms; the preparation of 10a -methyl-9a -steroids of the general formula V shown in the Figure wherein R2 and R4 have the above significance by oxidising 10a -methyl-9a -steroids of the general formula IV shown in the Figure wherein R2 and R2 have the above significance, QIV represents a secondary amine residue (including cyclic amine), or an O-acyl, alkyl or phenyl group and QV represents hydrogen, or both QIV and QV each represent a phenyl group or an aliphatic hydrocarbon group having from 1 to 6 carbon atoms; the preparation of 10a -methyl-9a -steroids of the general formula VIII shown in the Figure, wherein R2 and R4 have the above significance, R9 represents a hydrogen atom and R10 represents a hydroxy group, by reducing 10a -methyl-9a -steroids of the general formula VII with a reducing agent capable of reducing ketones to secondary alcohols (a 3-keto group converted to a 3-hydroxy group by this reduction step may be oxidised to a 3-keto group, for example, by means of manganese dioxide); the preparation of 10a -methyl-9a -steroids of the general formula VIII shown in the Figure wherein R9 represents a saturated or unsaturated hydrocarbon group containing from 1 to 6 carbon atoms or such radical containing one or more hydroxy or esterified hydroxy groups and/or double bonded oxygen atoms, and R10 represents a hydroxy or esterified hydroxy group, by reacting a 10a -methyl-9a -steroid of the formula VII with a Grignard compound or equivalent organo-metallic reagent of a saturated or unsaturated aliphatic halide having 1 to 6 carbon atoms or with an alkali metal acetylide having from 1 to 6 carbon atoms (in the latter case the process may include an additional step of partly or completely hydrogenating the unsaturated R9 group containing a triple bond) (a keto group present at the 3-position should be protected by converting to a 3-ether, enamine or glycol acetal to prevent attack by the organo-metal reagent and subsequently regenerating the 3-keto group).  The oxidation processes referred to above may be carried out with chromium trioxide, sodium, potassium or ammonium dichromate or potassium permanganate in an acidic or alkaline medium or with ozone in which case it is necessary to decompose the intermediate ozonide with oxidising agents such as hydrogen peroxide or alkaline permanganate or with reducing agents such as aldehydes, zinc dust and acetic acid, or iron powder and sulphuric acid.  It is preferable to protect a double bond at the 4,5-position when using the above oxidation methods such as by conversion to a 4,5-dibromide and then splitting off the bromine atoms, for example, by means of zinc dust in glacial acetic acid, or by conversion to a 4,5-epoxide and then decomposing the epoxide with a reducing agent, for example, a reducing agent referred to above, or with a solution of potassium iodide in acetic acid.  Hydroxy groups present at the 3- and/or 17-positions in the products of the above process may be esterified as required.  All the above processes may be modified in that the initial reactants are prepared by processes described in Specifications 929,273, 929,274 and 929,275.  In addition, the above processes or modified processes may be adapted to prepare any of the 10a -methyl-9a -steroids of the general formula I shown in the Figure and referred to above.  In the examples the compounds of formulae XXIII, XXIV and XXV shown in the Figure are prepared.  Therapeutic compositions contain as the active ingredients 10a -methyl-9a -steroids of the general formula I shown in the Figure, wherein R1 to R11 have the above significance, mixed with or dissolved or dispersed in a solid or liquid excipient.  The compositions may be administered orally or by injection, and have progestative, anabolic, antiinflammatory and anti-hormonal (such as anti-estrogenic or anti-androgenic) activities.