To describe and compare levels of physical activity and sedentary behavior in schoolchildren from 34 countries across 5 WHO Regions. The analysis included 72,845 schoolchildren from 34 countries that participated in the Global School-based Student Health Survey (GSHS) and conducted data collection between 2003 and 2007. The questionnaire included questions on overall physical activity, walking, or biking to school, and on time spent sitting. Very few students engaged in sufficient physical activity. Across all countries, 23.8% of boys and 15.4% of girls met recommendations, with the lowest prevalence in Philippines and Zambia (both 8.8%) and the highest in India (37.5%). The prevalence of walking or riding a bicycle to school ranged from 18.6% in United Arab Emirates to 84.8% in China. In more than half of the countries, more than one third of the students spent 3 or more hours per day on sedentary activities, excluding the hours spent sitting at school and doing homework. The great majority of students did not meet physical activity recommendations. Additionally, levels of sedentariness were high. These findings require immediate action, and efforts should be made worldwide to increase levels of physical activity among schoolchildren. Copyright (c) 2010 Mosby, Inc. All rights reserved.