99mTc MAG3 is the radiopharmaceutical agent that provides simultaneous investigation of renal perfusion, functional parenchyma and collecting system. Clearance of MAG3 which is equal to its tubular extraction rate (TER) and other quantitative parameters of renal function can be determined at the same time. The aim of the study was to analyze importance of TER, clearance index (CI) and renal accumulation rate (RA) of MAG3 in the assessment of the functional status of renal transplants. 31 kidney transplant recipients and 14 healthy donors were investigated. Dynamic renal scintigraphy was carried out 20 min. after i.v. injection of 150-220 MBq MAG3. Clearance was determined by single sample volume distribution method. For the calculation of CI and RA counts from transplant region acquired during the second minute of study were used. Results of TER, CI and RA were correlated with blood urea (Pu), serum creatinine (Pcr) and creatinine clearance (Ccr). The sensitivity of TER, CI and RA in well functioning kidney graft as well as in chronic rejection were analyzed. We concluded that: TER, CI and RA are more sensitive in comparison with Pu, Pcr and Ccr in quantitative assessment of renal transplant function; sensitivity of TER is greater than the sensitivity of CI and RA.