The knowledge of lymphocyte distribution is very usefulness in monitoring therapeutic treatments. We present here a method employed in clinical practice, the scintigraphy, to study in the rat the physiologic lymphocyte traffic. Rat T cells labeled with 99mTc were injected in syngeneic animals, and their fate was studied by serial scintigraphic scanning. Sorted naïve CD4+ CD45RC(bright) T cells homed to lymphoid organs and accumulated in spleen. CD4+ CD45RC(dim) memory lymphocytes first reached the liver and the lungs and recirculated. The results obtained by using the scintigraphic method to in vivo study the lymphocyte homing in rats are comparable to those obtained with previously used experimental methods. We consider the scintigraphic method a useful tool to in vivo track lymphocytes and to address therapeutic treatment in men.