A new formulation of a freeze-dried kit for the labeling of tetrofosmin with technetium-99m has been developed. The kit contains lyophilized mixture of 0.320 mg tetrofosmin [6,9-bis(2-ethoxyethyl)-3,12-dioxa-6,9-diphosphatetradecane], 0.025 mg stannous chloride dihydrate, 5 mg sodium tartrate and 5 mg sodium hydrogen carbonate. The product contains no antimicrobial preservative. When Tc-99m pertechnetate up to 6 mL saline containing 200 mCi is added to lyophilized mixture, a lipophilic, cationic Tc-99m complex is formed, Tc-99m-tetrofosmin. The performance of newly developed kit is compared with commercially available MYOVIEW kit for heart imaging. The patient studies show that the images of heart obtained by Tc-99m-tetrofosmin prepared by new formulation are equally good to MYOVIEW.