[en] 1-[14C] Hydroxymethyl-6-ethoxycarbonyl-5,7-dimethyl-4-phthalazone ([14C] EG-626) was synthesised from 6-ethoxy-carbonyl-5,7-dimethyl-4-methoxyphthalazine-2-N-oxide and potassium [14C] cyanide by the Reissert-Henze reaction. The overall radiochemical yield from potassium [14C] cyanide was 21.0 %. (author)