More than 10(11) killer cells are needed for adoptive immunotherapy, but it is difficult to obtain so many from patients. Peripheral blood lymphocytes (PBL) treated with lectin and then with recombinant interleukin-2 (rIL-2) give many lectin-induced lymphokine-activated killer (LILAK) cells, studied here for proliferation, cytotoxicity, IL-2 receptors (IL-2R) and subsets. PBL obtained from hepatoma patients or healthy adults were incubated with phytohaemagglutinin (PHA) or concanavalin A (ConA) for 3 days and with rIL-2 for 4 days. Then the medium was replaced with fresh medium containing rIL-2 every 3 or 4 days, with the volume increased as cells proliferated. Cytotoxicity was expressed as the percentage lysis of target cells by 4 h 51Cr release. LILAK cells from healthy adults increased 120-fold in 2 weeks when incubated with ConA; the lymphokine-activated killer (LAK) cells increased 7-fold. The percentage of IL-2R+ cells increased more with ConA than with rIL-2 alone. ConA induced more suppressor T cells than PHA. LILAK cells obtained from patients by PHA treatment increased 180-fold in 2 weeks. Their cytotoxicity to Daudi cells was 1% before culture and 91% in 2 weeks; that of LAK cells was 60%. LILAK cells were cytotoxic to the tumour target cells, but not to allogeneic PBL. Adoptive immunotherapy may become more practical if many LILAK cells can be obtained at once by large-scale culture, such as by a hollow-fibre system.