This report explores the potential of a simple pedometer for physical activity measurement and motivation, explaining that physical inactivity is one factor that has contributed to the recent obesity epidemic. After a brief history of the pedometer, the report discusses measurement, focusing on how to measure physical activity in free-living populations; what pedometers measure; the best type of pedometer to use; how to collect pedometer data (what unit of measure to use, how long the pedometer must be worn, and how to record step counts); and how many steps people take per day. Finally, the report discusses issues related to motivation, including how many steps people should take, how pedometers can be used to motivate and promote physical activity, and basing programs on theory. It notes that the essential elements of a program theory are problem definition, critical inputs, mediating processes, expected outcomes, extraneous factors, and implementation issues. The report concludes that pedometers are practical, accurate, and acceptable tools for measuring and motivation in physical activity and may be of practical importance in the war on obesity. (Contains 92 references.) (SM)