Tumor-specific T lymphocytes (CTL) are proliferated in vitro to induce by a stimulation with butanol-extracted soluble antigen (CBE) and human recombinant interleukin-2 (IL-2) from peripheral lymphocytes of cancer patients. Peripheral blood T lymphocytes (PBL-T), tumor infiltrating lymphocytes (TIL) and lymph node lymphocytes (LNC) from patients with colon cancer were stimulated in vitro with CBE and IL-2. Single stimulation with CBE (1 x 10(-3) micrograms/ml) also activated the proliferative response of the PBL-T (p < 0.01). On the other hand, high-dose (0.25-2 micrograms/ml) significantly inhibited the proliferation of the PBL-T that had been stimulated with 20U/ml IL-2 (p < 0.001). The IL-2 receptor expression of PBL-T, TIL and LNC was also activated with low-dose CBE and IL-2. The surface markers of stimulated lymphocytes responded anti-CD3 and CD8 monoclonal antibodies, but some TIL and LNC displayed CD3 and CD4 phenotype. The lymphocytes responding anti-CD8 monoclonal antibody possessed the cytotoxic activity against autologous tumor cells, but not the lymphocytes responding anti-CD4 monoclonal antibody. The results suggested that low-dose CBE and IL-2 augment the IL-2 receptor expression of T lymphocytes, thereby the proliferation of the antigen specific cytotoxic T cells.