The immunogenicity of human cancer cells transfected with interleukin 2 (IL-2) gene, a potent vaccine candidate, has not yet been fully investigated. Human renal cell carcinoma (RCC) cells transduced with human IL-2 gene (RCC-IL-2) were investigated in vitro for the capability to induce lymphokine-activated killer (LAK) or cytotoxic T lymphocyte (CTL) activity in peripheral blood mononuclear cells (PBMC) or tumor-infiltrating lymphocyte (TIL). The RCC-IL-2 cells stimulated PBMC to demonstrate LAK activity, and also stimulated autologous TILs to proliferate and exhibit cytotoxicity relatively restricted to autologous tumor cells. In contrast, both parental RCC and RCC transduced with neomycin gene alone failed to induce these activities. These results indicate that RCC-IL-2 cells are more potent than the other RCC cells with regard to inducing cytotoxic lymphocytes against autologous tumor cells.