H-3-Sch 58235 was prepared at a specific activity of 29.1 Ci/mmol by Ir(COD)(CY3P)PyPF6 catalysed exchange with tritium gas. C-14-Sch 58235 was prepared in three steps from p-hydroxy[ring-U-C-14]benzaldehyde with an overall radiochemical yield of 21%. C-13(6)-Sch 58235 was similarly prepared in three steps from p-hydroxy[ring-U-C-13(6)]benzaldehyde in an overall yield of 41%. Copyright (C) 2002 John Wiley Sons, Ltd.