Liposomes are small vesicles consisting of one or more concentric lipid bilayers enclosing discrete aqueous spaces. Liposomes potentially serve as carriers for radiolabels to visualize pathological processes scintigraphically. Research performed during the last two decades has revealed insight on the characteristics of liposomes with regard to their tissue distribution after i.v. injection. Various approaches have been developed to radiolabel liposomes with gamma-emitting radionuclides such as Ga-67, In-111 and Tc-99m. Preferably, liposomes are labeled according to the 'after-loading' method. The radionuclide can either be encapsulated in the aqueous interior or coupled to the lipid bilayer. The potential of radiolabeled liposomes to image infectious and inflammatory foci has been demonstrated in a variety of preclinical studies. Recently, a study in patients suspected of having infectious or inflammatory disease has been initiated. Preliminary clinically results exemplify the potential of Tc-99m-PEG liposomes to image infection and inflammation.