The effectiveness of "standard" lymphokine-activated killer (LAK) cells, recovered after 6 days, and of "standard" adherent LAK (A-LAK) cells, recovered after 14 days of culture in the presence of recombinant interleukin-2 (rIL-2) from peripheral blood lymphocytes of 21 healthy donors, was assessed through comparison of their proliferation, surface markers, cytotoxic activity, lymphokine production, and antitumor activity. In the presence of rIL-2, plastic adherent precursors of A-LAK cells proliferated much better than those of "standard LAK" cells and expanded even more than 300-fold. However, the final cell recovery of A-LAK was always lower because of their very few precursors, and the total lytic units (LUs) generated in A-LAK cultures were always lower for the same reason. On the other hand, the lytic activity of each A-LAK cell was always higher than that of a LAK cell. This was particularly evident on day 6 of culture. Removal of nonadherent cells after the first 24 h culture resulted in a significant enrichment in CD3-CD56+ and CD8+CD56+ cells in A-LAK cells, with a marginal number of CD4+ cells. A significant direct correlation between LUs and A-LAK CD3-CD56+ percentage was found. In the presence of rIL-2, A-LAK cells produced higher amounts of tumor necrosis factor-alpha and interferon-gamma than LAK cells, while only A-LAK cells produced IL-1 beta and small amounts of IL-4. Neither LAK nor A-LAK produced IL-2. In the absence of injections of IL-2, LAK and A-LAK cells were equally able to inhibit the growth of a human T-cell lymphoma in immunosuppressed nude mice.