The invention relates to a method of producing the radiolabeled aryl compound (I) Ar—X, or a salt thereof, wherein X is 211At, 210At, 123I, 124I, 125I, or 131I. The method involves reacting the aryl boronic acid compound (II) Ar—Y, or a salt thereof, wherein Y is a borono group (—B(OH)2) or an ester group thereof, with a radionuclide selected from 211At, 210At, 123I, 124I, 125I and 131I, in the presence of an oxidizing agent selected from an alkali metal iodide, an alkali metal bromide, N-bromosuccinimide, N-chlorosuccinimide and hydrogen peroxide, in water.