Researchers and practitioners require guidelines for using electronic pedometers to objectively quantify physical activity (specifically ambulatory activity) for research and surveillance as well as clinical and program applications. Methodological considerations include choice of metric and length of monitoring frame as well as different data recording and collection procedures. A systematic review of 32 empirical studies suggests we can expect 12,000-16,000 steps/day for 8-10-year-old children (lower for girls than boys); 7,000-13,000 steps/day for relatively healthy, younger adults (lower for women than men); 6,000-8,500 steps/day for healthy older adults; and 3,500-5,500 steps/day for individuals living with disabilities and chronic illnesses. These preliminary recommendations should be modified and refined, as evidence and experience using pedometers accumulates.