Twenty renal cell carcinomas were cultured in the presence of 200 IU/ml of recombinant interleukin-2; tumour-infiltrating lymphocytes (TIL) developed in 70% of cases; the phenotypic profile was heterogeneous in 11 TIL tested on day 30: 4 were mostly CD8 positive, 4 mostly CD4 and 3 showed CD4-CD8-CD56 mixed phenotypes. The cytotoxic activity was also heterogeneous, and no TIL developed a tumour-specific cytotoxic activity. The phenotypic profile and cytotoxic activity were also tested after thawing, and this study demonstrated that TIL can be frozen at the time of the nephrectomy, then thawed and cultured for the purposes of therapeutic trials when metastases appear. The differences between TIL derived from renal cell carcinoma and TI1 derived from melanoma are discussed.