The purpose of this study was to examine whether cardiovascular fitness, independent of confounding factors, was associated with immune responsiveness to clinically relevant challenges in older adults (60-76 years). Thirteen sedentary, low fit (LF; VO2max = 21.1 ± 1.1 ml^.Kg^-1.min^-1) and 13 physically active, high fit (HF; VO2max = 46.8 ± 3.4 ml^.Kg^-1.min^-1) older adults participated in this study. Dietary intake was assessed and a battery of psychosocial tests was administered. In vivo antibody and ex vivo proliferative and cytokine responses to influenza (Flu) and tetanus toxoid (TT) vaccination, and delayed-type hypersensitivity (DTH) skin tests were performed. HF elderly displayed a higher antibody response to 2 of the 3 strains included in the Flu vaccine as measured by hemagluttination inhibition, but there was no difference between groups in influenza-specific ex vivo proliferation or interferon(IFN)- or interleukin(IL)-10 production. HF elderly exhibited a lower IgG1 and a tendency for a higher IgG2 response to the TT vaccine. There were, however, no differences in TT-specific ex vivo proliferation or IFN- or IL-10 production. In contrast, HF subjects had higher proliferative responses to phytohemagluttinin. Lastly, there were no differences in DTH responses to fungal antigens between groups. These results suggest that, after accounting for confounding factors, HF elderly have higher antibody responses to Flu vaccine and a Th2 skewing of the antibody response to TT. There was little evidence that HF mounted better cell-mediated immune responses to the Flu or TT vaccine measured in peripheral blood cells or to other recall antigens in vivo.