A new approach to cancer therapy has been developed based on the adoptive transfer of autologous lymphokine-activated killer (LAK) cells and recombinant interleukin-2 (IL-2). Forty-one patients with advanced cancer who have failed all standard treatments were treated in this experimental protocol. Fourteen patients experienced an objective regression of cancer, including one patient with metastatic melanoma who underwent a complete regression. Objective responses were seen in patients with colorectal cancer, renal cell cancer, melanoma, and lung adenocarcinoma. The sites of tumor regression included subcutaneous tissue, lung, and liver. The major side effect of therapy resulted from the administration of high-dose IL-2 and was manifested primarily as fluid retention, resulting in a generalized capillary permeability leak syndrome. This approach to adoptive immunotherapy represents a promising approach to the therapy of patients with metastatic cancer. Attempts to increase the potency and decrease the toxicity of therapy and extend this treatment to patients with smaller tumor burdens are in progress.