Abstract: Objective To establish a useful and stable method for labeling insulin-like growth factor I analogue(IGF-1A) with ^99mTc. Methods The "pretinning" method was adopted to label IGF-1A. Several labeling conditions were tested. The volume of Tween 80 was from 0 to 10μl, the labeling efficiency was determined from 0.25 h to 6 h after labeling, SnCl₂·2H₂0 from 0.75g/L to 4g/L, the amount of IGF-1A from 20 to 100μg, ihe volume of ^99mTc perrhenate was from 10 to 200μL The in vitro stability of ^99mTc-IGF-IA was analyzed by using Iranian serum or sodium chloride as challenging agent, and the labeling efficiency was determined from 1 h to 24 h after added challenging agent. Results The labeling efficiency of ^99mTc-IGF-1A could reach(94.43±0.75)% and the mass fraction of radiocolloid was(3.47±0.71)%. It was(85.57±2.81)% after incubation 6h at room temperature, and was(54.07±3.86)% after incubation 24 h with human serum. Conclusions The optimum labeling method was 100μl stannous chloride(3g/L) dissolved in sodium gluconate, 40μl ICF-1A(2g/L), 300μl Na₃PO₄, 2μl 0.1% Tween 80, 50μl ^99mTc perrhenate, incubation 0.5h at room temperature, then added 500μl NaH₂PO₄. This method of labeling IGF-1A with ^99mTc using SnCl₂·2H₂O and sodium gluconate was stable and high labeling efficiency was obtained.