Aromatic halogen atoms, preferably iodine or bromine, but also chlorine are catalytically exchanged in the presence of a Pd catalyst, a base and tritium gas. The highest specific activity can be obtained by dehalogenation of aromatic iodine precursors (approx. 20-28 Ci/mmol, equal to 0.74 – 1.04 TBq/mmol), followed by bromine (approx. 14-25 Ci/mmol, equal to 518 – 925 GBq/mmol) and chlorine derivatives (approx. 8-16 Ci/mmol, equal to 296 – 592 GBq/mmol). Under these conditions fluorine atoms are not exchanged.