Abstract: The disclosed invention is drawn to the organometallic oestrogen complex of formula (I): ##STR1## in which A is a C.sub.1-7 alkylene radical or C.sub.2-7 alkenylene or alkynylene radical; M.sub.x is one or more identical or different transition metals; L'.sub.y is one or more identical or different ligands complexing the metal(s) of M.sub.x ; and L is a ligand for covalently coupling M.sub.x to A; and R is H or a C.sub.1-7 alkyl or alkoxy group which may be optionally substituted, particularly with one or more halogens. These complexes are useful for the treatment of hormone-dependent cancers. Also, when the metals of the complex M.sub.x are radioactive isotopes suitable for imaging, the complexes are useful as imaging agents.