Since to date very limited information on the distribution and function of the adenosine A(3) receptor is available, the development of a suitable radioligand is needed. Such a selective radioligand can then be used for quantitative autoradiography, preclinical studies in animals and subsequent human PET applications. Recently, a promising candidate compound, 5-(2-fluoroethyl) 2,4-diethyl-3-(ethylsulfanylcarbonyl)-6-phenylpyridine-5-carboxylate (FE@SUPPY), has been presented. The successful preparation of a suitable labelling precursor and the evaluation and optimization of the radiosynthesis of [F-18] FE@SUPPY is presented herewith. For satisfactory yields, a reaction temperature of 75 degrees C has to be applied for at least 20 min using 8-10 mg of precursor. Until now, 15 complete high-scale radiosyntheses were performed. Starting from an average of 51 +/- 12 GBq (average +/- SD; range: 30-67 GBq) [F-18]fluoride, 9.4 +/- 3.6 GBq of formulated [F-18]FE@SUPPY (32.3 +/- 12.4%, based on [(18)]fluoride, corrected for decay) were prepared in < 105 min.