99mTc-MAG, was synthesized, and biodistribution and blood clearance rate were compared with those of 131I- OIH in mice and rats respective]y. Finally renal image was obtained from a normal male volunteer before and after prescription of probenecid. The results obtained were as follows: 1) The uptalce of " Tc-MAG, by kindey was higher than that of 131I-OIH in mice 10 mins after injection (n=6, p<0.05), but slightly lower uptakes were found in all organs (kindney, blood, stomach, mtestinge and liver) 2 hrs after injection. 2) For "' Tc-MAG, t1/2 a=2.4-+0.0 min, t1/2B=44.3+7.4 min, and blood clearance=3.4+0.5ml/min, and for 131I-OIH t1/2=1.8=0.2 min, t1/2=69.1+9.5 min, and blood clearance=1.3+O.l min were found in rats. 3) From the renogram of normal male volunteer, we could find that tmax=130 sec and t1/2=430sec before probenecid prescriptiori, and tmax 150-170sec and t1/2=810- 1,170sec after probenecid prescriprion. From these results we concluded that " Tc-MAG, can be used instead of 131I-OIH for obtaining renal irnage.