[en] D-glucose-¹⁴C is enzymatically converted to uridine-diphospho-¹⁴C-D-glucose which in turn is oxidized by an enzyme reaction to uridine-diphospho-¹⁴C-D-glucuronic acid. The acid is separated from the reaction mixture using preparative paper chromatography. The interfering glucose phosphates and nucleoside-5'-phosphates are removed by the action of alkaline phosphatase in the presence of phenolphtalein acting as indicator. The advantages of the method of preparation include high yields attaining 85 to 95%, ease of product separation, time and material savings, and use of domestic raw materials. The acid molar activity exceeds 150 mCi/mmol. (M.D.)