Technetium-99m-d,l-hexamethylpropylene amine oxime (Tc-99m-HMPAO) has been developed in our Institute in order to meet the demand of GDR clinicians for a radiopharmaceutical, which allows the examination of regional cerebral blood-flow by SPECT. The present paper informs on synthesis and13C NMR spectroscopic identification of the ligand d,l-HMPAO as well as its labelling by reconstitution of a sterile, freeze-dried mixture containing d,l-HMPAO, stannous chloride, and sodium chloride with Tc-99m-pertechnetate eluate. Labelling efficiency (more than 90%, the lipophilic component 80–90%) and pattern of products were estimated using tlc and paper chromatography with a combination of three solvent systems. Quality control of the freeze-dried formulation includes methods for quantitative determination of the ligand and of stannous chloride. The ability of Tc-99m-HMPAO to be localized in brain was quantified in rats by organ distribution with time and by autoradiography, showing both high initial uptake, and blood flow-dependent distribution in the brain.