BACKGROUND: As a convenient and useful physical activity measurement tool,pedometer is widely used in research and intervention about physical activity of population. OBJECTIVE: To assess validity and reliability of the pedometer in measuring daily physical activity. DESIGN,TIME AND SETTING: The experiment was performed at the Department of Kinesiology,Nanjing Institute of Physical Education and Sports from April to June 2007. PARTICIPANTS: Thirty college students,15 majoring in Kinesiology and 15 majoring in social and physical education,15 females and 15 males,with an average age of (20?1) years,were selected from Nanjing Institute of Physical Education and Sports. METHODS: Participants wore a Digi-Walker200 for one week to record results of pedometer measurement,and filled in Bouchard Physical Activity Diary every day to note activity in 24 hours and calculate energy consumption. All participants completed International Physical Activity Questionnaire including large and moderate intensity activity,walking and sitting in a week. MAIN OUTCOME MEASURES: Daily steps,energy expenditure,sedentary time,waking time,exercise time,and weekly physical activity condition. RESULTS: Step counts were positively correlated with daily energy expenditure,walking time,and exercise time,and negatively related with sedentary time. Step counts of different physical activity levels were significantly different: more step counts could better reflect physical activity levels. Furthermore,exercise or continuous walking (more than 15 minutes) could significantly increase step counts. Daily physical activity including 30-minute moderate intensity activity could achieve or exceed the target steps of 10 000. CONCLUSION: Pedometer provides a useful and objective indicator of daily step counts assessing daily physical activity,but it is difficult to reflect activity intensity and patterns.