Abstract: Estrone and D. D. Q. are reacted to produce △9(11)-estrone by dehydrogenation reaction. With 5 % Pd/C as catalyst and dioxane as solvent, the estrone is tritiated by the addition of tritium gas, resulting in 3H-estrone which has a specific activity of 25 Ci/mM, and a radiochemical purity of 96%.