While exercise is generally recommended for older adults, the specific role of exercise in preventing falls and frail health is unclear. The Seattle FICSIT/MoveIt study is a population-based, randomized, controlled trial comparing the effects of three 6-month exercise interventions (endurance training, strength training, or combined endurance and strength training), and three 3-month endurance training interventions (stationary cycle, walking, or aerobic movement). Primary study outcomes are aerobic capacity, strength, gait, balance, and physical functional status. The study enrolls adults age 68-85 who have leg weakness and impaired gait. It differs from most previous community-based exercise studies in several respects: recruitment of subjects from a defined population; eligibility criteria based upon physiologic and functional status deficits; random assignment to exercise groups; assessment of both physiologic and functional status outcomes; follow-up beyond the completion of supervised exercise; and a large sample size (Total N = 180).