The purpose of this study was to test the hypothesis that regular exercise training in elderly people affects the type 1/type 2 balance. Nine elderly women who train by walking (mean+/-S.E.M., age 63+/-1 years, VO2 peak 32.2+/-1.0 ml kg(-1) min(-1)), 12 age-matched untrained women (63+/-1 years, 27.8+/-0.9 ml kg(-1) min(-1)), and nine young untrained women (26+/-1 years, 37.8+/-1.3 ml kg(-1) min(-1)) participated in the study. We measured interferon gamma (IFN-gamma), IL-2, and IL-4 in CD4+ and CD8+ T cells, to compare type 1 and type 2 T cells. The number of CD4+ cells expressing intracellular IFN-gamma (CD4+/IFN-gamma cell) significantly higher in the elderly trained than in the young (P<0.01). The number of CD8+/IL-2 cells was significantly higher in the elderly trained than in the elderly untrained (P<0.05). The number of CD8+/IL-4 cells was significantly higher in the young than in the elderly untrained (P<0.01). No significant differences were apparent in the IFN-gamma/IL-4 ratio within CD4+ and CD8+ cells from the three groups. These results might indicate that the effect of age on the balance of type 1/type 2 T cells was stronger than the effect of physical training.