Physical fitness affects our ability to function and be active. At poor levels, it is associated with such health outcomes as diabetes and cardiovascular disease. Physical fitness testing in American youth was established on a large scale in the 1950s with an early focus on performance-related fitness that gradually gave way to an emphasis on health-related fitness. Using appropriately selected measures to collected fitness data in youth will advance our understanding of how fitness among youth translates into better health. In Fitness Measures and Health Outcomes in Youth, the IOM assesses the relationship between youth fitness test items and health outcomes, recommends the best fitness test items, provides guidance for interpreting fitness scores, and provides an agenda for needed research. The report concludes that selected cardiorespiratory endurance, musculoskeletal fitness, and body composition measures should be in fitness surveys and in schools. Collecting fitness data nationally and in schools helps with setting and achieving fitness goals and priorities for public health at an individual and national level.