SUMMARYFresh (uncultured) TIL from 12 untreated patients with primary renal cell carcinoma were prepared from tumour specimens by enzymatic digestion, and were characterized by immunotluorescence using MoAbs recognizing leucocyte differentiation antigens or particular Va or V/? segments of the T cell receptor (TCR). These fresh TIL comprised CD3+ (20-84%); CD4+ (3-15%); CD8+ (13-35%); a/3TCR^ (20 50%); 7<5TCR+ (3-17%); CD16+ (1-18%) and CD56( 3-10%) cells. Significant proportions of VQ2"', V^5.1+ and V^6+ cells were found in TIL of certain patients with renal cell carcinoma, suggesting that they comprised oligoclonal T cells. T cell lines were developed in low concentrations of rIL-2 (200 U/ml) from TIL from II patients wiih renal cell carcinoma, and were characterized by immunofluorescence and cell-mediated cytotoxicity. These T cell lines consisted primarily of CD3^ (51-94%); CD4+ (1 80%); CD8+ (0-84%); Q/3TCR+ (65-87%); 7^TCR+ (0-25%); CDI6+ (0-16%) and CD56+ (2-57%) cells. These Tcell lines exhibited non-specific cytotoxicity against autologous and aliogeneic renal tumour cells, with the exception of one T cell line that exhibited preferential cytotoxicity against autoiogous renal tumour cells. These results suggest that fresh TIL from patients with renal cell carcinoma contain significant proportions of oligoclonal T cells that may have accumulated at the tumour site as a result ofa clonal expansion.