Four thousand men and women 65 years and older living in the community participated in a health survey between 2001 and 2003. Information was collected regarding self-perceived ranking of social status in terms of income, education, and occupation; history of chronic diseases; smoking habit; and physical activity of all types using the Physical Activity Scale for the Elderly.3 Body mass index was measured. A venous blood specimen was also collected, and leukocyte DNA was extracted for determination of telomere length using quantitative polymerase chain reaction methods4 and calibrated against samples with telomere length determined by standard Southern blot analysis of terminal restriction fragments. Specimens were analyzed for the first 976 men and 1030 women in the cohort (mean [SD] age, 72.8 [5.0] and 72.0 [5.2] years, respectively). The association between telomere length and quartiles of physical activity level was examined using analysis of covariance adjusting for age and other potential confounding factors (body mass index, smoking, and self-perceived socioeconomic status). The statistical package used was SAS version 9.1 (SAS Institute Inc, Cary, North Carolina), and the association was also tested for linear trend using the General Linear Model.