The organ distribution study and the whole body scan were done in the albino rats at intervals of 5, 30, 60, 90 and 120 minutes after the intravenous injection of 99Tc-pertechnetate absorbed in Sephadex beads of 20~80 micra in diameter. Effect of additional injection of physiological saline and saline absorbed in Sephadex beads of 20~80 micra in diameter on the scan and organ distribution were also studied. The results were as follows. 1. Five minutes after the injection of 99Tc-pertechnetate absorbed in Sephadex beads of 20 ~80 micra in diameter, Sephadex was well trapped in the lungs, with which the excellent lung scan was obtained. Two hours after the injection, kidneys were well visualised instead of lungs, which suggested that kidney acts as the excretory organ. Five minutes prior to scan, additional injection of physiological saline absorbed in Sephadex above mentioned was done. The bladder was also well visualized together with the kidneys. 2. In the distribution studies, most of radioactivity was detected in the lungs at 5 minutes and was gradually transferred chiefly to the kidneys and bladder and partly to the liver. 3. Additional injection of physiological saline resulted in a rapid transfer of 99Tc trapped in the lung to both the kidneys and liver. 4. Additional injection of physiological saline absorbed in Sephadex beads of 20~80 micra in diameter resulted in a rapid transfer of Tc trapped in the lung to only the urinary system. 5 .Results of these studies suggested that ; a) Other nutrients and therapeutic compounds may be carried into the lungs along with Sephadex beads and then released in high concentration, which would exert greater therapeutic effect locally than that of the usual administration b) Some radionuclides absorbed in Sephadex could be used as the lung scan agents, the flushing out of which by Sephadex-saline also give satisfactory renal and bladder scane. c) Other potent therapeutic radionuclides could be retained for some time by this method, which can be in the lungs easily flushed out within 2 hours.