This publication describes the general scope of a Co-ordinated Research Project focused on the optimization of syntheses, quality control, in vitro and in vivo evaluation of F-18 and I-123 radiopharmaceuticals based on peptides with known or anticipated clinical potential. Selective labelling procedures using prosthetic groups were applied to both fluorine and iodine. Studies included investigation on the fate of the label, stability in vivo, biodistribution and pharmacokinetic studies in rodents and in cell culture. With respect to I-123, the work aimed at development of a simplified labelling kit using solid state systems.