The purpose of this study was to examine the relationship between active versus inactive lifestyle and immunocompetence in older women. A sample of 46 independently dwelling, ambulatory and mentally alert women 60-98 years was examined, 25 who rated themselves as active and 21 who rated themselves as inactive . Lymphocyte subpopulations were analyzed by flow cytometry using selected monoclonal antibodies. The self-reported active subjects (also validated by their current unsolicited participation in a formal exercise class) demonstrated significantly higher percent change in CD25 mitogen stimulated lymphocytes (P = 0.0335) than those who reported themselves to be sedentary.