Aging mammalians show reduced expression and induction of cytoprotective heat shock proteins in response to physiological stresses. Physical training can increase Hsp72 expression in young and old animals, but whether same adaptations can be observed in old people remains unknown. We hypothesized that the maintenance of physical activity during aging should preserve Hsp72 expression in leukocytes of elderly people. Intracellular and surface Hsp72 (the inducible form of Hsp70) expression in leukocytes as well as apoptotic and necrotic leukocytes were measured by flow cytometry at rest and after maximal incremental test on treadmill in the following groups: 8 young subjects (25.3+/-0.6 year, G25), 12 sexagenarians (66.2+/-1 year, G65) and 9 octogenarians (82.2+/-1.2 year, G85), all physically active. Protein and lipid oxidation markers were also measured at rest and post-exercise. Results showed significant lower basal percentages of Hsp72-positive lymphocytes in G85 compared to G25. At rest, lower mean fluorescence intensity in Hsp72-positive monocytes was measured in G65 and G85 compared to G25, and in granulocytes from G85 compared to G25. Maximal exercise test induced systemic oxidative-stress in the three groups but did not induce any increase in apoptotic or necrotic cells. We observed a significant increase in the percentage of Hsp72-positive lymphocytes from G85. This study showed that maintaining physical activity during aging can preserve the ability to induce Hsp72 in response to physiological stress.