We have studied the kinetics of the antigen induced response of naive and memory CD8 T cells expressing a transgenic T cell receptor (TCR) specific for the glycoprotein peptide amino acid 33 – 41 (GP33) of the lymphocytic choriomeningitis virus (LCMV). Memory T cells were generated in vivo by adoptive transfer of LCMV TCR transgenic T cells into normal recipient mice, followed by LCMV infection. The results demonstrated that the cell cycle progression and kinetics of TCR down‐modulation, CD25 and CD69 up‐regulation were identical in naive and memory T cells after antigen recognition. Moreover, the two T cell populations did not differ in respect of activation thresholds and in their proliferative capacities neither in vitro nor in vivo. However, memory CD8 T cells could be more rapidly induced to become cytolytic and to secrete high levels of interleukin‐2 and interferon‐γ than naive T cells. LCMV GP33‐specific CD8 memory T cells were only slightly more efficient in reducing LCMV titers in the spleen but were far more effective than naive LCMV GP33‐specific T cells in controlling subcutaneous tumor growth of B16.F10 melanoma cells which expressed the LCMV GP33 epitope as tumor‐associated antigen. Thus, in our experiments the main difference between CD8 memory T cells and naive cells is the ability of the former to rapidly acquire effector cell functions.