[en] In order to evaluate the blood perfusion in the transplanted kidneys, sup(99m)Tc-DTPA dynamic studies were performed 53 times in 25 cases of various stages (normal function 31, acute rejection 11, chronic rejection 8, ATN 2 and ureteral obstruction 1). Seven parameters were calculated from the Tc-DTPA dynamic studies. (A) Mean transit time (MTT): the time interval between the positive and negative peaks in the first order differential curve (Oldendorf's method). (B) Appearance time: the time interval from injection to the positive peak of differential curve. (C) T max: the time from injection to the maximum. (D) T sub(1/2) max: the time to half maximum. (E) Slope: the time interval between 10% to 90% of the maximum counts in the initial slope. (F) Uptake ratio: ratio of the RI counts in the region of the kidney over the counts in the whole field during the MTT. (G) Kidney/Background ratio. The results of this study were as follows. Significant prolongation of MTT and marked decrease of Uptake ratio were recognized during acute rejections (p < 0.001). T max, Slope and K/B ratio were also significantly changed (p < 0.05, p < 0.005, p < 0.01). In the chronic rejection group, all of the seven parameters revealed significantly different from those of the normal grafts. As to the correlations between the kidney function (creatinine clearance) and the parameters, MTT and Uptake ratio were highly correlated to Ccr (r = -0.736 and r = 0.625, respectively). In conclusion, MTT and Uptake ratio were the most valuable parameters in detecting the rejection episodes and evaluating the kidney function. (J.P.N.)