Adoptive immunotherapy is an approach to cancer treatment that has not received significant evaluation in cancer patients. Recent developments in modern cellular immunology have expanded the opportunities for utilizing adoptive immunotherapy in humans. A variety of animal models have been developed utilizing the adoptive transfer of immune cells that can mediate the regression of established murine tumors. Analyses of these models are defining the important criteria necessary for the application of this approach to humans. Studies of the immune response of human cells to autologous tumors are identifying cells with antitumor reactivity that may be of value in the treatment of human malignancy. Preliminary clinical studies have been performed demonstrating the feasibility of infusing large numbers of activated lymphoid cells into humans. Adoptive immunotherapy is an approach to the treatment of cancer that deserves further study.