Immune functions of peripheral blood (PBL), regional lymph node (RLNL), and tumor infiltrating lymphocytes (TIL) were evaluated in lung cancer patients. PBL had many natural killer (NK) cells and the highest NK activity, and it showed the highest augmentation of NK activity by interferon-gamma (IFN-gamma) + recombinant interleukin-2 (rIL-2) among the three groups of lymphocytes. PBL had high lymphokine-activated killer (LAK) activity of against a broad spectrum of cell lines and moderate activity against autologous tumor cells by increased effector to target (ET) ratio but the lowest ability of IL-2 production of the three groups of lymphocytes. The RLNL not associated with tumor metastasis had a few NK cells and lower NK activity than PBL, but its LAK activity was almost the same but not greater than that of PBL. RLNL had the highest ability of IL-2 production among the three groups of lymphocytes. All activities of RLNL associated with tumor metastasis were lower than those not associated with tumor metastasis. TIL exclusively consisted of T-cells, especially cytotoxic/suppressor T-lymphocytes. NK activity and lymphocyte blastogenesis of TIL were lower than those of other groups. The LAK activity of TIL differed greatly with the case, and it was the highest against autologous tumor cells among the three groups of lymphocytes in three of eight cases. These findings showed that PBL, RLNL, and TIL had characteristic subpopulations of lymphocytes and different functions of host immune responses in lung cancer. Efficient augmentation of the characteristic immune responses will lead to a more effective total cancer therapy.