Labeling of disodium dihydrogen 1-hydroxyethane-1,1-diphosphonate (HEDP) with 188Re was studied. Stannous chloride was used as a reducing agent for the reduction of 188ReO4 –. The dependence of the yield of 188Re–HEDP complex upon the HEDP concentration, tin(II) content, reaction time, amount of antioxidant, pH, reaction temperature, and presence of carrier was examined. The optimum conditions ensuring high labeling yield of 188Re–HEDP complex (91.0% with carrier-free Re and 96.5% with carrier-added Re) are as follows: 15 mg of HEDP, 2 mg of Sn(II), 4 mg of ascorbic acid, pH 1.2, 100°C, 10 min. The amount of the carrier added is 200 μg of KReO4. The 188Re–HEDP complex prepared at 100°C is more stable than that prepared at 30°C, and the carrier-added 188Re–HEDP complex is more stable than the no-carrier-added complex.