We cultured lymph node lymphocytes (LNL) from lung cancer patients in the presence of recombinant interleukin 2 (rIL2). The ability of LNL to respond to rIL2 was not affected by the advance of cancer stage when tested for proliferation and for lymphokine-activated killer (LAK) activity. The LAK activity of LNL was comparable to that of the corresponding peripheral blood lymphocytes. The rIL2-induced proliferation of macrophage-depleted LNL was augmented by the reconstitution with autologous alveolar macrophages while the LAK activity was not affected. However, macrophage-reconstituted LNL expanded rapidly and reached higher cell densities and exhibited a significantly lower LAK activity than macrophage-depleted LNL. The diminished LAK activity in macrophage-reconstituted LNL were markedly augmented by the subculture at a low cell density. From these results, we conclude that LNL can be a good material for the postoperative LAK therapy and that macrophage is useful in culture of LAK cells.