Interleukin 2 has provided the means of generating activated lymphocytes from the tumor-bearing host which show in vitro anti-tumor activity. These cells can be derived either from a ubiquitous null cell precursor population, exhibiting promiscuous lysis of nearly all tumors after culture in IL2 (ie. the LAK cell) or from a T cell precursor population infiltrating tumors and showing some relative specificity for lysis of the autologous tumor following activation (ie. TIL). When utilized in murine cellular adoptive immunotherapy models, both LAK cells and TIL are able to display marked anti-tumor effects against established micrometastatic tumor. LAK cells have been subsequently employed in adoptive immunotherapy against metastatic human tumors and in a limited number of cases have been able to mediate the regression of advanced cancers of differing histologies. The role of adoptive immunotherapy as standard therapy of human tumors will depend on refinement of the methodology and progress toward increased efficacy and reduced toxicity. TIL may possess theoretical advantages in these areas and efforts are currently proceeding to evaluate these new anti-tumor reagents in the the treatment of patients with cancer.