The current gold standard for imaging infection is radiolabeled white blood cells. For reasons of safety, simplicity and cost, it would be desirable to have a receptor-specific ligand that could be used for imaging infection and that would allow a differential diagnosis between sterile and septic inflammatory processes. Ligands tested for this purpose include labeled peptides ( Tc-labeled f-Met-Leu-Phe, I-IL-1ra, Tc-IL-8, Tc-P483H, Tc-P1827DS, Tc-C5ades- Arg, Tc-RP517, 111In-DPC11870-11), human polyclonal antibodies, monoclonal antibodies, antibody fragments, antimicrobial agents (ciprofloxacin, sparfloxacin, ceftizoxime, isoniazid, ethambutol, fluconazole, all labeled with 9 Tc), antimicrobial peptides and bacteriophages. Radiolabeled antibodies represent a valid alternative to labeled white blood cells under specific conditions and indications. Radiolabeled antibiotics and antimicrobial peptides are promising candidates for an infection-specific radiopharmaceutical. However, at present we still need to investigate many basic aspects to better understand the mechanisms of binding and accumulation of this class of radiopharmaceuticals to bacteria.