Lymphocytes from the mesenteric lymph nodes (MLN) of mice were enriched for CD4+ and CD8+ T cell populations, labeled with (51Cr) sodium chromate, and transferred to the bloodstream of syngeneic recipients. The time course of migration of the labeled cells from the blood to the secondary lymphoid organs of the recipients was investigated. CD4+ and CD8+ subpopulations differed in their profile of appearance in different lymphoid organs. Computer assisted analysis of the observations was used to obtain quantitative estimates of the rate of clearance of the lymphocytes from the blood into the tissues, and the rate of departure of the cells from the tissues. In the spleen, CD4+ lymphocytes were cleared from the blood about one and one-half times faster than CD8+ lymphocytes, but the CD8+ cells were retained longer. Inguinal nodes (IN), MLN, and Peyer's patches (PP) showed a consistent ability to clear CD4+ cells from the blood at a rate approximately 2.5 x greater than that for CD8+ cells, but the retention of the lymphocytes in these tissues varied with lymphocyte phenotype and the organ concerned. CD4+ lymphocytes were retained longer in PP and MLN than in IN, whereas CD8+ cells were retained longer in IN and MLN nodes than in PP. We conclude that the rate of clearance of lymphocytes into secondary lymphoid organs from the blood varies in a regular way with T cell phenotype and that organ specific sorting of T subpopulations also proceeds after the cells are admitted to the tissues.