The potential utility of tumor-infiltrating lymphocytes (TIL) in the adoptive immunotherapy of human tumors has been suggested by murine experiments showing these cells to be 50-100 times more powerful than LAK cells in treating advanced metastatic disease. A method for the large-scale expansion of human TIL for the use of these cells in clinical trials is described in this report. TIL were successfully expanded on an experimental scale from 24 of 25 consecutive human tumors, including six melanomas, ten sarcomas, and eight adenocarcinomas. Tumors were digested enzymatically to yield single cell suspensions which were cultured in RPMI 1640 medium with 10% human serum and 1000 U/ml recombinant interleukin-2. Lymphocytes constituted from 3% to 74% of single cell tumor suspensions, and expanded from 2.9-fold to 9.1 X 10(8)-fold over a culture period ranging from 14 to 100 days. Nine of 24 TIL cultures lysed fresh autologous tumor targets in 4 h chromium release assays. Cell surface phenotyping identified cultured TIL as activated cytotoxic/suppressor T cells. Subsequently, large-scale expansion of TIL was successful in generating more than 10(10) lymphocytes in five of eight consecutive cases. Clinical trials employing the adoptive transfer of expanded TIL to patients with metastatic disease have begun.