The preparation of ^99m Tc-complexes with twenty derivatives of (2RS, 4R)-1,3-thiazolidin-4-carboxy- lic acid over a broad pH range (1.5–8.9) is described for a potential use in radiodiagnostic medicine. The labelling efficiency was checked by paper and thin layer chromatography and for all well-soluble compounds is higher than 90 %. Paper electrophoresis and gel chromatography indicated the presence of two types of complexes differing in charge and molecular mass. The structure of both types of the ^99m Tc-complexes is also discussed. The organ distribution and its time dependence were determined in mice after i.v. application.

        Key words: radiodiagnostics – ^99m Tc-complexes – derivatives of thiazolidin-4-carboxylic acid