Tumor-infiltrating lymphocytes (TIL's) were isolated from human glioma biopsy specimens by immunomagnetic separation using T cell-specific monoclonal antibodies coupled to paramagnetic beads, and were expanded in culture with feeder cells and interleukin-2 (IL-2). The infiltrating cells from five of seven patients proliferated in culture. When tested after 2 to 3 weeks of culture, virtually all of the cells stained with antibodies against the CD2 and CD3 antigens. Most cells also expressed human leukocyte antigen class II molecules, while varying percentages of cells stained with antibodies against the IL-2 receptor and the CD4 and CD8 antigens. The cytotoxicity of the cultured TIL's against autologous and allogeneic glioma cells and the K562 and Daudi cell lines was measured and compared with that of lymphokine-activated killer (LAK) cells from the same patients. None of the TIL's showed significant cytotoxicity against these targets, whereas LAK cells lysed all of the targets.