CD62L⁻ T cells lose alloreactivity over time on transfer into allogeneic but not syngeneic recipients. Bone marrow cells (1 × 10⁷) from Rag2^−/−γC^−/− B6 mice and CD62L⁻ T cells (1 × 10⁶) from unprimed B6 CD45.2 mice were transplanted into lethally irradiated BALB/c (A and Bii, allogeneic) or Rag2^−/−γC^−/− B6 (Biii, syngeneic) recipients. BALB/c-origin BCL1 cells (5 × 10⁵) were injected into bone marrow recipients at different times after transplantation (Ai, day 7; Aii, day 14; Aii, day 21; B, day 28). The recipient mice were monitored for development of leukemia/lymphoma and survival. For Vβ family experiments (C), peripheral blood was obtained from allogeneic or syngeneic recipients of CD62L⁻ T cells (same as B without BCL1 cell challenge) more than 100 days after transplantation. Percentages of Vβ⁺ cells were determined by flow cytometry. Each group contained 10 to 12 mice. The data were pooled from 2 independent experiments with similar data (*P < .05, normal BALB/c vs other groups; #P < .05, normal C57BL/6 vs CD62L⁻ [allogeneic]).