99mTc complexes of 2-ethyl-2-hydrobutyric acid, 2-hydroxyisobutyric acid and (+)- and (-)-citramalic acid are readily prepared in high yield and high purity by reduction of 99mTcO4- in the presence of excess ligand. The resulting agents are very stable in vitro, but can undergo some decomposition during chromatographic analysis unless appropriate precautions are taken. Biodistribution studies in rats and dogs show that these new 99mTc agents accumulate primarily in the kidney and urinary bladder.