Abstract Memory T cells are known to be less sensitive to depletion therapies than naïve T cells. We tested whether anatomical location of memory T cells determines their resistance to depletion. We injected naïve B6 mice with rabbit anti-mouse lymphocyte serum, ALS. Two days after the last injection, more than 95% of CD8 and 60-80% of CD4 T cells were depleted from lung, liver, bone marrow, peripheral blood and spleen, but not from the thymus, with the residual cells being predominantly CD44hi. The in vivo binding of rabbit IgG to T cells in ALS-treated mice did not necessarily correlate with the depletion efficiency. Residual CD4 T cells were isolated from various organs and intravenously injected into groups of ALS-treated or control IgG-treated B6 mice. The distribution of injected cells in the adopted hosts was similar regardless of their origin. The CD4 T cells from lung, liver and thymus were further depleted when relocated into circulation, suggesting that their location is critical in the depletion resistance. The greatest depletion was observed within spleen and liver of the ALS-treated adopted hosts implicating these organs as possible sites of depletion. However, CD4 T cells obtained from BM and spleen were not further affected by relocation suggesting that they are intrinsically resistant to depletion. Understanding the phenotype and functions of depletion-resistant memory T cells from different organs may guide the use of lymphodepletion in transplant patients.