The invention comprises 16a -(alkyl, alkenyl, and alkynyl)-17b -ol and 16b -(alkyl, alkenyl and alkynyl)-17a -ol steroid compounds of the general formula <FORM:0909373/IV (b)/1> in which there is one double bond in the 4(5) or 5(10) position and wherein R represents hydrogen or an alkyl radical having less than 9 carbon atoms or an alkylacyl radical in which the alkyl portion contains less than 8 carbon atoms, R1 represents an alkyl, alkenyl or alkynyl radical having less than 9 carbon atoms, and R11 represents hydrogen or an alkylacyl radical in which the alkyl portion contains less than 8 carbon atoms; a process for the preparation of steroid compounds of the general formula <FORM:0909373/IV (b)/2> wherein R and R1 have the above significance, by isomerising 5(10)-estrene compounds of the general formula <FORM:0909373/IV (b)/3> wherein R and R1 have the above significance, with an acid (this process may be modified by treating a 3-alkoxy-16-alkyl, alkenyl or alkynyl-2,5(10)-estradiene-16,17-diol or the corresponding 17-ether with mild acid to form a 5(10)-estrene of the above general formula which may or may not be isolated before forming the 4-estrene by continuing the acid treatment-a 17b -(2-pyranyl)oxy ether may also be used in which case the 4-estrene product contains a 17b -hydroxy group), and when R represents the alkylacyl radical, acylating the product with the required acid anhydride; a process for the preparation of compounds of the general formula <FORM:0909373/IV (b)/4> wherein R1 represents an alkyl or alkenyl radical containing less than 9 carbon atoms, by hydrogenating compounds of the general formula <FORM:0909373/IV (b)/5> wherein R11 represents an alkenyl or alkynyl radical containing less than 9 carbon atoms; a process for the preparation of compounds of the general formula <FORM:0909373/IV (b)/6> wherein R represents hydrogen, an alkyl radical containing less than 9 carbon atoms or an alkylacyl radical in which the alkyl portion contains less than 8 carbon atoms, R1 represents an alkyl, alkenyl or alkynyl radical containing less than 9 carbon atoms, and R11 represents hydrogen or an alkylacyl radical in which the alkyl portion contains less than 8 carbon atoms, by hydrolysing compounds of the general formula <FORM:0909373/IV (b)/7> wherein A represents an alkyl or acyl radical, and R, R1 and R11 have the significance indicated immediately above. The 16- and/or 17-esterified 5(10)-estrenes of the above general formula are prepared by acylating with one equivalent of an acylating agent to form the 17-monoester or with two equivalents to form the 16,17-diester, or by selectively hydrolysing the 16,17-diester to form the 16-monoester. The 16-substituted-16,17-dihydroxy-4-estrene-3-ones of the above general formula may be 17-monoacylated, or diacylated, e.g. with isopropenyl acetate followed by hydrolysis of the group in the 3-position of the resulting 16-substituted-3,16b ,17b -triacetoxy-3,5-estradiene. 3-Alkoxy-16-alkyl, alkenyl or alkynyl-2,5(10)-estradiene-16,17-diol or the corresponding 17-ether is prepared by a Birch type reduction, i.e. with lithium and ammonia, of the corresponding 3-alkoxy-16-alkyl, alkenyl, or alkynyl-1,3,5(10) - estradiene - 16,17 - diol or 17-ether thereof. 3,17b -Dimethoxy-16a -propyl-1,3,5(10) - estratrien-16b -ol is prepared by reacting 3-methoxy - 16a - propyl - 1,3,5(10) - estratriene-16b ,17b -diol with potassium t-butoxide and then with methyl iodide. 3-Methoxy-16a -propyl-17b -ethoxy-1,3,5(10)-estratrien-16b -ol is prepared by a similar method. 3 - Methoxy-16a -ethynyl-17b -(2-pyranyl)oxy-2,5(10) -estradien-16b -ol is prepared by reducing 3-methoxy - 17b - (2-pyranyl)oxy-1,3,5(10)-estratrien-16-one with sodium borohydride to form 3-methoxy-17b -(2-pyranyl)oxy-1,3,5(10)-estratrien-16b -ol, reducing this compound with sodium and ammonia to form 3-methoxy-17b -(2-pyranyl)oxy-2,5(10)-estradien-16b -ol, oxidising this compound by the Oppenauer method to form 3-methoxy-17b -(2-pyranyl)oxy-2,5(10)-estradien-16-one, and reacting this compound with potassium acetylide to form the desired product. 3-Methoxy - 16a - (1-octynyl)-17b -(2-pyranyl)-oxy-2,5(10)-estradien-16b -ol is prepared by reacting 1-octyne magnesium bromide and 3-methoxy-17b -(2-pyranyl)oxy-2,5(10) - estradien16 - one. 3 - Methoxy-16a -(2-methallyl)-17b -(2-pyranyl)oxy-2,5(10) -estradien-16a -ol and 3-methoxy-16a -allyl-17b -(2-pyranyl)oxy - 2.5(10)-estradien-16b -ol are prepared by a similar method. 3-Alkoxy-16a -alkyl, alkenyl or alkynyl-estra-3,5-diene-16b ,17b -diol is prepared by treating 3-methoxy - 17b - (2-pyranyl)oxy-2,5(10)-estradien-16-one with hydrochloric acid to form 17b -hydroxy-4-estrene-3,16-dione, treating this compound with an alkyl orthoformate to form 3-alkoxy-17a -hydroxy-3,5-estradien-16-one, and treating this compound with an alkyl, alkenyl or alkynyl metallic reagent such as an alkyl magnesium halide or an alkyl lithium. 3-Methoxy - 16a - octyl-17b -(2-pyranyl)oxy-2,5(10)-estradiene-17b -ol 16-monoacetic ester is prepared by passing ketene gas into a solution of 3 - methoxy - 16a - octyl-17b -(2-pyranyl)oxy-2,5(10)-estradien-16b -ol. 3 - Methoxy - 16a - octyl-2,5(10)-estradiene-16b ,17b -diol 17-monoacetic ester and 16,17-diacetic ester are prepared by reacting 3-methoxy-16a -octyl-2,5(10)-estradiene - 16b ,17b -diol with one and two equivalents respectively of acetic anhydride. The 16,17-diacetic ester may be selectively hydrolysed to form the 16-monoacetic ester. The process is applicable to the preparation of the 3-alkoxy-16a -substituted-2,5(10)-estradiene-16b ,17b -diol, 16- and 17-monoacylates and 16,17-diacylates.