A series of C7-substituted estra-1.3,5(10),6-tetraene-3,17 beta-diols were prepared as. precursors to radiodiagnostic agents of breast cancer. The introduction of the olefin moiety at C6/C7 in the molecules was achieved through thermal elimination of the 6-hydroxy group in the corresponding estra-1,3,5(10)-triene-3,17 beta-diols.