Immunotherapies using high doses of interleukin-2 and tumor-infiltrating lymphocytes (TIL) have been developed for the treatment of advanced cancer. Current efforts are aimed at enhancing the therapeutic efficacy of TIL through genetic modification. Initially, we demonstrated that retroviral-mediated gene transfer into TIL using a neomycin resistance marker gene was practical and safe for use in patient therapy. Because TIL have been shown to localize at tumor sites, we are now introducing the TNF gene into TIL in an attempt to increase the local concentrations of TNF in the tumor microenvironment without inducing systemic toxicity. Another gene being studied for insertion into TIL is a chimeric antibody/T-cell receptor gene. For many histologic types of cancer, it is relatively difficult to obtain specific TIL, but many monoclonal antibodies (mAb) exist that bind tumor-associated antigens. In order to combine the effector function of T cells with the antitumor specificity of antibodies, we have constructed chimeric receptor genes containing the variable region domains from mAb linked to T-cell signal-transducing chains. Human TIL retrovirally transduced with a chimeric receptor gene constructed from an anti-ovarian cancer antibody were redirected to recognize and lyse ovarian cancer cell lines specifically. This approach may allow adoptive immunotherapy against histologies not previously amenable to this treatment modality.