Apoptosis, which leads to a fall in HIV-1 specific T cell count, is considered to be one of the HIV-1- specific CTL escape mechanism of HIV-1. Detecting epitope-specific CD8 T cells has become possible, by using a tetramer of 4 HLA class I molecules combined with epitopes. We first made numerous tetramers using a large number of identified epitopes, and then with these tetramers, we analyzed HIV-1 specific CD8 T cells in patients with HIV-1. The results revealed that there were many HIV-1-specific CD8 T cells in patients with chronic HIV-1 infection. Also, 4-color analysis using antibodies specific for CD27, CD28, and CD45RA showed that HIV-1-specific CD8 + T cells in patients with chronic HIV-1 infection expressed a memory/effector phenotype with CD28- CD45RA-. Moreover, 5-color analysis demonstrated that HIV-1-specific CD8 T cells expressed CD 27low CD28- CD45RA-. These results indicate that HIV-1 epitopes are continuously presented by HIV-1 infected cells. Currently, we are investigating abnormality of HIV-1-specific CD8 T cells in function and differentiation in patients with chronic HIV-1 infection.