The invention comprises a compound having the general formula: <FORM:0864381/IV (b)/1> wherein R is a alkyl or aryl radical, R1 is a hydroxy or keto group, R11 is iodine, hydrogen or the group -O-SO2-R111 wherein R111 is a lower alkyl radical of one to three carbon atoms inclusive, phenyl, tolyl, or naphthyl provided that when R11 represents iodine or the group -O-SO2-R111 wherein R111 is as above defined, R1 represents a keto group, and a process for the preparation thereof wherein a compound having the formula: <FORM:0864381/IV (b)/2> is treated with an organic sulphonyl halide to obtain a compound having the formula: <FORM:0864381/IV (b)/3> wherein R111 is a lower alkyl radical having 1-3 carbon atoms inclusive, phenyl, tolyl, or naphthyl and then if desired treating the latter compound with an alkali metal iodide to produce the corresponding 21-iodo derivative, if desired dehalogenating to produce a compound having the formula: <FORM:0864381/IV (b)/4> Alternatively 6-methyl-9a -fluoro-11b , 17a -dihydroxy-21-iodo-1, 4-pregnadiene-3, 20-dione is dehalogenated to obtain 6-methyl-9a -fluoro-11b , 17a -dihydroxy-1, 4-pregnadiene-3, 20-dione, which if desired may be oxidised to the corresponding 11-hydroxy compound. As organic sulphonyl halide there may be used methane sulphonyl chloride, toluene sulphonyl chloride, toluene sulphonyl bromide, benzene sulphonyl chloride and a and b -naphthylsulphonylchloride. The 21-iodo compound may be reduced with thiosulphates, bisulphates and sulphites, of sodium and potassium, or by zinc and acetic acid. Oxidation may be effected with chromic anhydride, n-bromoacetamide, or n-bromosuccimide. Examples describe the preparation by the process above of (1) 6a -methyl-9a -fluoro-11b , 17a , 21-trihydroxy-1, 4-pregnadiene-3, 20-dione 21-methane sulphonate, (2) 6a -methyl-9a -fluoro-11b , 17a -dihydroxy-21-iodo-1, 4-pregnadiene-3, 20-dione, (3) 6a -methyl-9a -fluoro-11b , 17a -dihydroxy-1, 4-pregnadiene-3, 20-dione, (4) 6a -methyl-9a -fluoro-17a -hydroxy-1, 4-pregnadiene-3, 11, 20-trione, (5) compounds corresponding to the products of example 1-4 in which the 6-alkyl group is methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl or phenyl and the 6b -epimers; Example (6) describes the preparation of 6a -methyl-9a -fluoro-11b , 17a -dihydroxy-1,4-pregnadiene by treating 6a -methyl-11b , 17a -dihydroxy-1, 4-pregnadiene-3, 20-dione with n-bromacetamide to obtain a D 9,11 compound, which is subsequently converted to the corresponding 9a -bromo, 9(11)-oxido and finally 9a -fluoro compounds. Example 7 describes the introduction of a double bond in 1, 2-position into 6a -methyl-9a -fluoro-11b , 17a -dihydroxy-4-pregnene-3, 20-dione by means of Septomyxa affinis. Specification 863,781 is referred to.ALSO:The invention comprises oral, parenteral and topical compositions incorporating 6-alkyl or 6 - aryl - 9a - fluoro - 11b ,17a - dihydroxy - 1,4-pregnadiene - 3,20 - dione or 6 - alkyl or 6-aryl-9a - fluoro - 17a - hydroxy - 1,4 - pregnadiene-3,11,20-trione. Tablets for oral usage employ either polyethylene glycol 4000 or 6000 as a carrier or lactose and/or sucrose as a diluent. For topical application the compounds may be used in ointments, lotions, jellies, creams, suppositories, bougies and aqueous suspensions. A dermatological and ophthalmic ointment has the following composition: wool fat, mineral oil, 6a -methyl-9a -fluoro-11b ,17a -dihydroxy-1,4-pregnadiene-3, 20-dione, and white petrolatum. An antibiotic such as neomycic sulphate, bacitracin, circulin, polymyxin B sulphate, gramicidin, streptomycin sulphate, dihydrostreptomycin sulphate, oxytetracycline, tetracycline, chlorotetracycline, and chloramphenicol and the sulphonamides may also be added to such ointments. Specification 863,781 is referred to.