Purpose: We analysed Tc-99m-MAG3 renal scans to evaluate renal function of transplanted kidney and to detect various renal transplant complications, measuring the ratio of renal radioactivity at three minutes to that at 20 minutes(elimination index). Material and Methods: The fifty seven renal transplantation recipients were studied. There were 50 normal functioning transplanted kidneys as group I and 7 abnormal functioning transplanted kidney, including 5 cases of acute renal rejection, 2 Gases of acute tubular necrosis as group II. The protocol consisted of: (1) Tc-99m-MAG3 740MBq injection intravenously; (2) sequential imaging for 2min(60two-second images) followed by 30min(30 sixty-second images); (3) drawing of region of interest(ROI) on renal imaging; (4) time- activity curves were generated from renal ROI after background subtra ction, and time of maximum activity(Tmax) and half time of maximal peak radioactivity(T1/2) were produced in the renogram curve. (5) EI through Bischof-delaoye method as determined on the renogram curve. Results: Normal group(I) shows mean EI of 2.21(95.0% Confidence limit of 2.01-2.87), Tmax, of 154 sec, t1/2 of 1,139 sec. Abnormal group(II) shows mean EI of 0.74, Tmax of 1,466 sec, t1/2 of 19,224 sec. The EI, Tmax, T1/2, BUN and serum creatinine values are significantly different between normal group(I) and abnormal group(II) (p 〈0.0001). Conclusion: By measuring EI-with Tc-99m- MAG3, renal function of transplanted kidney could be easily evaluated and various complications could be detected early.