Assessment of physical functioning in older persons has generally focused on identifying and characterizing subjects at the disabled end of the functional spectrum. This paper examines the validity of objective, standardized performance measures of physical functioning in characterizing the hierarchy of functioning in non-disabled, higher functioning older persons. Data are from 1192 participants aged 70-79 years in The MacArthur Research Network on Successful Aging Field Study. Participants were drawn from three community-based populations and represented the upper tertile of functioning, based on cognitive and physical screening assessments. The cohort showed a great deal of heterogeneity on most of the performance measures of functioning that were used. Several analyses provided evidence that this variability was not random and that the performance measures were valid measures of functioning in this cohort: 1) individual performance measures showed a moderate degree of correlation with each other; 2) a summary measure of performance showed an association with chronic diseases and other factors known to be associated with health status; and 3) a larger group than expected by chance alone was found to be functioning at the very highest level.