An oestrogen having the empirical formula C20H22O and designated "miroestrol" is prepared by subjecting a methanol or ethanol extract of tuberous roots of pueraria mirifica to partition chromotography. The oestrogen reduces Fehling's solution, is destroyed by alkali, gives an anhydro-derivative C19H20O5 with hydrochloric acid, gives a monomethyl ether, melts with decomposition at 270 DEG  C. and has an optical rotation of [a ]17 DEG  = + 301 DEG . Powdered roots of pueraria mirifica are first extracted with aqueous methanol or ethanol then with pure methanol or ethanol and the combined extracts evaporated to dryness.  The residue is taken up with methanol and after standing, the granular precipitate is filtered off and the filtrate evaporated to dryness.  This residue is dissolved in methanol and ether is added with the formation, on standing, or a gummy precipitate.  The supernatant solution is decanted, evaporated to dryness and the residue again treated with methanol and ether as before.  The precipitate which formed is dissolved in methanol and re-precipitated with ether and the combined supernatant solutions evaporated to dryness.  Ethyl acetate was added and the solution left to clarify, the filtrate was evaporated to dryness and partitioned between benzene, ethyl acetate, methanol and water. The lower phase was evaporated to dryness and the residual chromotographed on a large Kieselguhr column using benzene and ethyl acetate as the mobile phase and methanol and water as the stationary phase.  Aliquots of the various fractions were examined by paper chromatography and an oestrogen-rich fraction rechromatographed on a smaller column.  After two such treatments, the fractions containing the oestrogen partially crystallized and the oestrogen was re-crystallized from methanol. Specifications 137,051, 453,583, [both in Group VI], and U.S.A. Specification 2,112,712 are referred to.ALSO:A process for the production of an oestrogen comprises subjecting a methanol or ethanol extract of tuberous roots of pueraria mirifica to partition chromatography.  It was formerly thought that the roots producing the oestrogen were of the species butea superba, and an oestrogen has been described by Butenardt of empirical formula C19H20O6 isolated from these roots.  In the Specification the oestrogen is designated "miroestrol" with an empirical formula C20H22O6 but is said to be identical with that described by Butenhardt.  Powdered roots of pueraria mirifica are first extracted with aqueous methanol or ethanol, then with pure methanol or ethanol and the combined extracts evaporated to dryness.  The residue is taken up with methanol and after standing the granular precipitate is filtered off and the filtrate evaporated to dryness.  This residue is dissolved in methanol and ether is added with the formation, on standing, of a gummy precipitate.  The supernatant solution is decanted, evaporated to dryness and the residue again treated with methanol and ether as before.  The precipitate which forms is dissolved in methanol and reprecipitated with ether and the combined supernatant solutions evaporated to dryness.  Ethyl acetate was added and the solution left to clarify, the filtrate was evaporated to dryness and partitioned between benzene, ethyl acetate, methanol and water. The lower phase was evaporated to dryness and the residue chromatographed on a large Kieselguhr column using benzene and ethyl acetate as the mobile phase and methanol and water as the stationary phase.  Aliquats of the various fractions were examined by paper chromatography and the oestrogen-rich fractions rechromatographed on a smaller column. After two such treatments the fractions, containing the oestrogen, partially crystallized and the oestrogen was recrystallized from methanol, melting with decomposition at 270 DEG  C.  Specifications 437,051, 453,583, and U.S.A.  Specification 2,112,712 are referred to.