Dynamic studies of kinetics of 99mTcO4, 57Co-Bleomycin, 67Ga, A2 fraction of 57Co-Bleomycin in Yoshida sarcoma bearing rats were undertaken. Then the regional variations of rate of the initial uptake of a radiopharmaceutical were examined using functional representation of the rate constants as a function of position. It was concluded that--for radiopharmaceuticals with a high initial uptake rate--the method resulted in visualization of tumor and in suppression of the blood background, within five to eight minutes after administration. This approach based on an evaluation of the parameters of the radiopharmaceutical kinetics in organs and tumor makes possible the use of short-lived radionuclides for tumor visualization and could offer some possibilities of distinguishing the tumor from other accumulating organs.