Labeling of ethylenediamine–N,N,N,N-tetrakis (methylene phosphonic) acid (EDTMP) with rhenium-188 was investigated. Stannous chloride was used as a reducing agent for the reduction of 188ReO4-. Dependence of the yield of 188Re-EDTMP complex upon the concentration of EDTMP, tin(II) content, reaction time, amount of antioxidant, pH, reaction temperature and adding of carrier was examined. The optimum condition that gives high labeling yield of 188Re-EDTMP complex (95.8% with carrier-free rhenium and 97% with carrier- added rhenium) was achieved using 40mg EDTMP, 0.8mg Sn(II), pH = 0.8, reaction temperature 100oC and 5 min reaction time. The amount of carrier added equal to 200g KReO4- Furthermore, 188Re-EDTMP complex prepared at 100oC is more stable than that prepared at 30oC and the carrier added 188Re-EDTMP complex is more stable than the no carrier added complex.