Attempts are being made to develop adoptive immunotherapeutic techniques utilizing the transfer of cells grown in long-term culture interleukin-2. Techniques for the prolonged growth of cytotoxic and proliferative T cell lines and clones with anti-tumor reactivity have been developed. These cells have been shown to mediate the immunologic rejection of allografts and syngeneci tumors and attempts to use these cells in the adoptive immunotherapy of mouse and human tumors are in progress. A new class of cytotoxic cells has been described in both the mouse and the human. The lymphokine activated killer (LAK) cells develop selective cytotoxicity for cancer cells into mice bearing established turmors can mediate the inhibition of pulmonary and hepatic metastases. The systemic administration on interleukin-2 has been shown to enhance immune responses in vivo. In the past year, a new immunotherapeutic trial began studying the effects of adoptive transfer of lymphokine activated killer cells and recombinant IL-2 into patients with advanced cancer. Six objective responses have been seen in 12 evaluable patients including one complete response in a patient with malignant melanoma.