Lymphocytes from peripheral blood, lymph node, spleen and tumour of 7 patients with various carcinomas (2 lung, 3 colon, 1 gastric and 1 parotid tumour) were cultured for 15 days in conditioned media containing T-cell growth factor (TCGF; Interleukin 2) after which their cytotoxic activity against autologous tumour (and in some instances, autologous normal) cells and allogeneic tumour targets was evaluated in a short-term 51Cr-release assay. Significant cytotoxicity against autologous tumour targets was detected in at least one effector preparation from all of the patients, under conditions where, in some cases, other autologous cells (normal lung, PHA-transformed lymphocytes) were resistant. This cytotoxicity also generally extended to allogeneic tumour targets, but lysis of K562, a cell line sensitive to natural killing, occurred in only 3 of 19 effector cell preparations. The data are consistent with a polyclonal expansion of cytotoxic T-cells of tumour-bearing patients which includes the amplification of a population recognitive of antigens expressed on autologous neoplastic cells.