Adherent lymphokine-activated killer (A-LAK) cells, selected from peripheral blood lymphocytes (PBL) of normal human donors by adherence to plastic, and cultured in the presence of interleukin 2 (IL-2), are highly enriched in CD3-CD56+ natural killer (NK) cells. These IL-2-activated NK cells proliferate extensively upon further culture in conditioned medium containing IL-2. In contrast, we previously found that with PBL of some patients with advanced cancer, the same procedure often failed to yield high enrichment of NK cells or substantial expansion in the numbers of these effector cells. To obtain sufficient numbers of A-LAK cells for adoptive immunotherapy in cancer patients, an improved method for generation of human A-LAK cells with irradiated mitogen-stimulated allogeneic PBL- or Epstein-Barr virus-transformed lymphoblastoid cell lines was introduced. In paired experiments, A-LAK cultures with feeder cells showed significantly enhanced IL-2-driven proliferation of A-LAK cells obtained from normal donors or patients with metastatic melanoma, renal cell carcinoma, and other types of solid cancers. The growth-promoting effect of feeders for A-LAK cells resulted in significantly improved expansion of CD3-CD56+ (NK) effector cells in A-LAK cultures established from normal donors. Cells in these cultures also had significantly higher levels of antitumor cytotoxicity against K562 and Daudi targets than did A-LAK cells grown in the absence of feeder cells. Enrichment in CD3-CD56+ cells and antitumor activity also occurred in patient A-LAK cultures supplemented with mitogen-stimulated feeder cells, but was not statistically significant. Overall, despite improved proliferation and CD3-CD56+ cell content of A-LAK cultures established in the presence of mitogen-activated feeder cells, only 39% (21/54) of patients tested generated A-LAK cells that would be judged acceptable for large-scale therapeutic use by criteria based on fold expansion and purity of A-LAK cells. These results suggest that in comparison to normal individuals, NK cells of many patients with advanced solid tumors are defective in their ability to respond by proliferation to IL-2 even in the presence of exogenously supplied growth factors.