With the aim of making direct investigational studies of various liver functions of sustained healthy animals, we devised operative procedures which are not only simple and reproducible but also adaptable to experiments even over the course of one-week without anesthesia. Using rats which have been operated upon, three kinds of tracers, 99mTc-pool scinti, 99mTc-pertechnetate and 99mTc-phytate, were recorded by a scintillation camera with a single-photon system immediately after intraportal administration. The results revealed that the discharge of these radioactive components from the hepatic vein began 0.2s after the administration, that the maximum intrahepatic concentration was reached between 2 and 5 s thereafter, and that 10 s later, these radioactive components were returned to the liver after their systemic circulation. Intrahepatic uptake of these three tracers was about 20% for all radioactivities administered.