[21-C-11]Progesterone was synthesised via the cross-coupling 17 beta-carboxylic acid chloride-4-androsten-3-one with lithium [C-11]methyl(2-thienyl)cuprate (LiCN). The title compound was obtained in 30-35% decay corrected radiochemical yield, based on [C-11]methyl iodide, within 35 minutes after end of radionuclide production. The specific radioactivity was 14 GBq/mu mole. (21-C-13)Progesterone vias synthesised using the same procedure for determination of the position of the label.