• Lymphokine-activated killer cells are thought to be important mediators of host tumor defense. In the present study, the cytotoxic potential of lymphokine-activated lymphocytes against different head and neck squamous cell carcinoma cell lines was investigated. Lymphokine-activated killer cells were derived from peripheral blood lymphocytes. Effector peripheral blood lymphocyte cell suspensions were incubated in the presence or absence of recombinant interleukin-2. Cytotoxicity of incubated cells or fresh peripheral blood lymphocytes was determined in a 3-hour chromium 51 release assay. Target cell lines included K562 (a natural killer–sensitive target) and the following head and neck squamous cell carcinoma cell lines: Cal 27, UMSCC-1, UMSCC-8, UMSCC-16, UMSCC-19, and UMSCC-22a. Fresh peripheral blood lymphocytes and peripheral blood lympho