Allogeneic tumor-specific lymphocytes can mediate tumor regression after intensive lymphodepleting preparatory regimen. C57BL/6 mice bearing B16 tumors were left untreated (A) or irradiated with 9 Gy TBI (B). Mice were left untreated as a control (NT) or injected on day 0 with vaccinia virus encoding hgp100 and exogenous IL-2 (VI) or injected with 10⁶ or 10⁷ (as indicated) allogeneic pmel-1^b/d cells, vaccine, and IL-2 (PVI). *P < .001. **P < .05. All groups received syngeneic BMT with 10⁶ unsorted bone marrow cells the day after the transfer of the effector cells (day 1). Results of tumor area are the mean of measurements of at least 5 mice per group (± SEM). Data are representative of 4 independent experiments.