A process for the production of [.sup.18F]-TAFDG can produce
[.sup.18F]-TAFDG in a high radiofluorination yield. A process for the
production of an organic compound labeled with radioactive fluorine
includes the steps of preparing a reaction solution containing
[.sup.18F]fluoride ions, a phase transfer catalyst, potassium ions,
1,3,4,6-tetra-O-acetyl-2-O-trifluoromethanesulfonyl-.beta.-D-mannopyranos-
e as a labeling precursor compound and a solvent, and giving a reaction
condition to the reaction solution to obtain
1,3,4,6-tetra-O-acetyl-2-[.sup.18F]fluoro-2-deoxyglucose, in which the
solvent contains water.