To implement effective non-communicable disease prevention programmes, policy makers need data for physical activity levels and trends. In this report, we describe physical activity levels worldwide with data for adults (15 years or older) from 122 countries and for adolescents (13—15-years-old) from 105 countries. Worldwide, 31·1% (95% CI 30·9—31·2) of adults are physically inactive, with proportions ranging from 17·0% (16·8—17·2) in southeast Asia to about 43% in the Americas and the eastern Mediterranean.