Solutions of glucoheptonate and sodium pertechnetate (Tc-99m) were subjected to electrolysis at various ampere-time products until a charge was found that consistently promoted tagging of greater than 90% efficiency. It was found that 9 coulombs (100 mA, 90 sec) consistently yielded a final product that contained less than 10% total radiochemical impurities (unbound pertechnetate and reduced, hydrolyzed technetium). Radiochemical purity of the final product was established using a two-solvent thin-layer chromatographic system with methyl-ethyl ketone and normal saline as the solvents. The tagging efficiency and stability of the tagged complex were determined with similar chromatographic analysis. It was shown that use of a 15% solution of calcium glucoheptonate resulted in a more stable product than that prepared from commercially available stannous glucoheptonate. The rapid, accurate chromatographic method for determination or radiochemical purity of the product is described. The final product is considered equal or superior to commercial Tc-99m (Sn) glucoheptonate and was produced at considerably less cost.