New specificities may be engrafted onto lymphocytes by the transfer of genes for chimeric receptors that combine antigen recognition and signal-transducing elements. We have engineered and evaluated a new class of chimeric receptors that use the natural ligands of receptors found to be frequently overexpressed by cancer cells. The heregulin molecule, a ligand for Her3 and Her4 receptors when fused with the CD3 zeta-chain, was capable of redirecting T lymphocytes to recognize and respond to cancer cell lines that overexpress these receptors. Thus, CD8+ T lymphocytes were isolated from a healthy individual and transduced to express the chimeric heregulin-zeta receptor. These modified effector cells acquired the ability to specifically lyse a breast cancer cell line that overexpresses Her3 and Her4. A new class of chimeric receptors, such as heregulin-zeta, endowing anti-cancer effector cells with the potential to recognize and eliminate tumor targets, are likely to increase the effectiveness of adoptive immunotherapy for the treatment of cancer.