The memory/activated T cells, which mediate the long‐lived host response against tuberculosis, in mice immunized with either bacillus Calmette–Guérin (BCG) or mycobacterium heat‐shock protein 65 (hsp 65) antigen expressed from plasmid DNA (DNA‐hsp 65), were characterized. Protection against Mycobacterium tuberculosis challenge by DNA‐hsp 65 vaccination was associated with the presence of lymph node T‐cell populations in which CD8⁺/CD44^hi interferon‐γ (IFN‐γ)‐producing/cytotoxic cells were prominent even after 8 or 15 months of plasmid DNA‐mediated immunizations, whereas after BCG vaccination the majority were CD4⁺/CD44^lo IFN‐γ‐producing T cells. When the cells were separated into CD4⁺CD8⁻ and CD8⁺CD4⁻ and then into CD44^hi and CD44^lo types, CD44^lo cells were essentially unable to transfer protection in adoptive transfer experiments, the most protective CD44^hi cells were CD8⁺CD4⁻ and those from DNA‐vaccinated mice were much more protective than those from BCG‐immunized mice. The frequency of protective T cells and the level of protection were increased up to 8 months and decreased after 15 months following DNA or BCG immunizations.