We studied subsets and cytotoxicity of recombinant interleukin-2 (rIL-2)-expanded tumor-infiltrating lymphocytes (TIL) from renal cell cancer (RCC) patients. TIL were successfully expanded in 13 of 14 RCC cases using anti-CD3 during the initial 48 h of culture. Percentages of CD8-positive cells among rIL-2-expanded TIL at 1-4 week(s) of culture were 56.2 +/- 15.1% (range 26.2-79.8%, n = 13) and not necessarily predominant over CD4-positive cells. Natural killer and lymphokine-activated killer (LAK) activities of TIL at 3-6 weeks of culture were 31.6 +/- 15.8% (range 1.4-57.4%, n = 9) and 16.6 +/- 11.6% (range 3.8-35.6%, n = 6), respectively. Autologous and allogeneic RCC cytotoxicity of TIL at 3-4 weeks of culture were 17.9 +/- 19.7% (range 0-47.6%, n = 4) and 18.9 +/- 14.8% (range 0-47.3%, n = 12), respectively. Since there was no statistical difference between them, autologous specific cytotoxicity was not demonstrated. From these result of the present study, it is unlikely that most of effector cells of rIL-2-expanded TIL in autologous RCC lysis are major histocompatibility complex-restricted cytotoxic T cells. We concluded that it is doubtful whether TIL is significantly superior over LAK cells in immunotherapy of human RCC.