 To refine key trial design benchmarks including sample size calculations to demonstrate the feasibility of a full-scale trial and refiningdeveloping recruitment, procedures, materials and organizational infrastructure, the LIFE Lifestyle Interventions for Independence in Elders study conducts a pilot, single-blind, randomized, controlled trial involving comparison of a physical activity program of moderate intensity to a successful aging program. Approximately 400 sedentary persons aged 70 to 90 years who are at risk of disability are followed for at least one year at four intervention sites: Wake Forest University School of Medicine in Winston Salem, NC; the University of Pittsburgh in Pittsburgh, PA; the Cooper Institute in Dallas, TX; and the Stanford University in Palo Alto, CA. The Administrative Coordinating Center and the Data Management and Quality Control Center are at Wake Forest University School of Medicine. 