Preventing or delaying the onset of physical frailty is an increasingly important goal because more individuals are living well into their 8th and 9th decades. We describe the development and validation of a functional fitness test battery that can assess the physiologic parameters that support physical mobility in older adults. The procedures involved in the test development were (a) developing a theoretical framework for the test items, (b) establishing an advisory panel of experts, (c) determining test selection criteria, (d) selecting the test items, and (e) establishing test reliability and validity. The complete battery consists of 6 items (and one alternative) designed to assess the physiologic parameters associated with independent functioning—lower and upper body strength, aerobic endurance, lower and upper body flexibility, and agility/dynamic balance. We also assessed body mass index as an estimate of body composition. We concluded that the tests met the established criteria for scientific rigor and feasibility for use in common community settings.