The MAG3 is a tubular excreting radiopharmaceutical for renal image. We synthe-sized benzoyl MAG3 (Bz-MAG3) and made a kit for labeling with Tc-99m. We checked the labeling effeciency of Tc-99m labeled MAG3 and biodistribution. Labeling efficiency was checked by TLC- SG (acetonitrile/H2O=2/1). After injecting of 1 mCi of Tc-99M-MAG3 to ICR-mice, Tmax(min), T1/2(min) were obtained in the renogram. Sequencial images (30sec, 2min, 5min, 10min, 15min, 20min) of TC-99m-MAG3 were compared with those of commercial Tc-99m-DTPA (Du Pont Merck Pharmaceutical Co.) kit. 1) The Rf value of synthesized Tc-99m-MAG3 was 0.78 and labeling efficiency was 97.5¡¾1.9% (n=10). 2) The dynamic images of the Tc-99m-MAG3 were better than those of the Tc-99m-DTPA. 3) The Tmax(min.) and T1/2(min.) of Tc- 99m-MAG3 (n=10) were 1.5¡¾0.5 (left), 1.4¡¾0.4(right), and 4.3¡¾1.4 (left), 4.8¡¾2.0 (right), respectivel. The Tmax(min.) and T1/2(min.) of Tc-99m-DTPA (n=7) were 2.7¡¾1.6 (left), 2.7¡¾1.6 right), and 3.8¡¾1.7 (left), 4.5¡¾2.7 (right), respectively. The quaility of image and labeling efficiency of the synthesized Bz-MAG3 kit were excellent, that it was supposed to be used in routine clinical work.