The expression of γ/δ T cell antigen receptors (TcR) in T cell lines or clones derived from tumor-infiltrating lymphocytes (TIL) from patients with solid tumors was investigated. γ/δ TcR T cell lines were derived from TIL from patients with Wilms tumor, sarcoma or metastatic melanoma by stimulation with autologous tumor cells alone and recombinant interleukin 2 and they exhibited nonspecific cytotoxicity against autologous and allogeneic tumor cells, or cells of the K562 or the MEL21 tumor cell lines. Two T cell lines were derived from a patient with Wilms tumor. One of them expressed a non-disulfide-linked γ/δ TcR using the 60-kDa γ chain, whereas, the other expressed a disulfide-linked γ/δ TcR. A T cell line was derived from a patient with sarcoma and expressed a disulfide-linked γ/δ TcR, whereas, a T cell line derived from a patient with melanoma expressed a non-disulfide-linked γ chain of 62 kDa. Several T cell clones were developed from patients with metastatic melanoma or Wilms tumor and expressed either disulfide- or non-disulfide-linked γ/δ TcR. Northern analysis of RNA from certain of these clones revealed a full-length γ chain transcript, whereas, the α or β chain transcripts were either absent or truncated. These T cell clones exhibited nonspecific cytotoxicity. Both disulfide- and non-disulfide-linked TIL T cell lines and clones expressed the δ TCS1 determinant. γ/δ TcR+ cells in freshly prepared TIL from these patients were present in low proportions (<5%) and their δTCS1/δ1 ratios were within the range observed in the peripheral blood of normal donors. These results demonstrate that both disulfide-and non-disulfide-linked γ/δ TcR are expressed on T cell lines and clones derived from TIL from solid tumors. Non-disulfide-linked γ/δ TcR using the 56–66-kDa γ chain are frequently found on TIL-derived T cell lines and clones. These 56–66-kDa γ chains are rarely expressed on T cell lines or clones derived from peripheral blood lymphocytes of normal donors.