Lymphokine-activated killer (LAK) cells generated by culture of regional lymph node cells (LNC) with interleukin 2 (IL 2) for 4 and 11 days were examined for their functional capabilities in comparison with those of peripheral blood mononuclear cells (PBM) in 25 patients with gastric carcinoma. The cytotoxic activity of LAK cells induced from LNC for 4-day culture with IL 2 was significantly lower than that from PBM. However, the LNC-LAK cytotoxicity was markedly increased up to almost the same level as that of PBM after l l-day culture. The production of interferon-? (INF-y) and tumor necrosis factor-a (TNF-a) from nonadherent LAK cells in LNC was also significantly reduced as compared to that from PBM 4 days after culture, when stimulated with or without tumor target, Raji cells. After 1 1-day culture with IL 2, however, the levels of these cytokines produced by LNC-LAK cells either with or without stimulation by tumor target were comparable to those by PBM-LAK cells, although the release of these cytokines was markedly reduced when compared to that after 4-day culture. Phenotypic analysis revealed decreased proportion of cells mediating NK activity in LNC before and 4 days after culture. CD56+ and CD57+ cells in LNC were increased after 11-day culture, although the percentages of these cells were still low as compared to those in PBM. The proportions of OKIal+ and CD25+ cells were uniformly increased after 4 and 11-day culture in both cell populations. Changes in subpopulations of CD4+ and CD8+ cells in LNC were not apparently different from PBM. These results indicated the differential LAK cell function of cells from regional lymph nodes from PBM in patients with gastric carcinoma.