Development of Tc-99m labelling strategies can be useful in the preparation of infection imaging agents by laboratories in Member States. With techniques that were developed for the testing of label stability in vitro and in vivo, with the laboratories participating in the project becoming proficient in labelling the chosen molecules with Tc-99m using a variety of techniques, and with in vivo and in vitro quality assurance measurements standardized by all participants and applied, Tc-99m agents were viewed as reliably labelled. Additionally, with the identification of Tc-99m ubiquicidin peptide 29–41 as a radiolabelled agent with potential clinical utility, the project has made a major contribution to nuclear medicine by providing the first convenient Tc-99m labelled ‘specific’ infection imaging agent.