The prevalence and increasing trends of obesity in Spain are a matter of concern. In adults, the prevalence of obesity and overweight is 14·5 and 38·5 %, respectively, whereas in children and adolescents it is 13·9 and 26·3 %. This situation prompted the Spanish Ministry of Health and Consumer Affairs to draw up the Strategy for Nutrition, Physical Activity and the Prevention of Obesity (NAOS), which aims to improve the diet and encourage the regular practice of physical activity by all citizens, with special emphasis on children. Coordinated by the Spanish Food Safety Agency and the General Directorate of Public Health, a wide range of stakeholders participated in drafting the Strategy through a broad consultative process. Anchored on the core goal of adopting a lifelong perspective in the prevention and control of obesity, NAOS encompasses recommendations for action in four fields: family and community, schools, private sector, and the health system. Launched on 10 February 2005, the Strategy will undergo careful monitoring and evaluation. A newly created Obesity Observatory will carry out epidemiological surveillance, define indicators to measure impact of interventions, facilitate the exchange of experiences among different initiatives, identify research priorities, monitor adherence and application of the self-regulation agreements, and conduct rigorous evaluation of initiatives to identify those that are successful and should be prioritized. To our knowledge, NAOS is the first strategy of its kind in Europe and we recommend it as an example to be followed by countries that, like Spain, face the challenge of combating the pervasive epidemic of obesity.