Eleven lymphocyte clones were established from the peripheral blood lymphocytes of a patient with gliosarcoma by means of autologous tumor stimulation and the limiting-dilution technique with recombinant interleukin-2. Ten of the 11 clones were cytotoxic against the autologous tumor cell line GI-1. Seven of the 10 clones were also cytotoxic against allogeneic brain-tumor lines and HeLa cells, one clone was cytotoxic against several target cells, and two clones were specifically cytotoxic against GI-1 and allogeneic brain-tumor cells. One of the 11 clones was not cytotoxic against any target cells tested. Lymphokine-activated killer cells induced by recombinant interleukin-2 alone exhibited cytotoxic activity against all target tumor cells tested. Surface phenotypic analysis revealed that all lymphocyte clones expressed CD3 antigen, some expressed CD4 antigen, and others expressed CD8 antigen. These clones seemed to be antigen-specific cytotoxic T lymphocyte clones. Analysis with these antigen-specific cytotoxic T lymphocyte clones may be useful in the elucidation of tumor-specific or tumor-associated antigens on autologous tumor cells.