This paper summarises recent past and current international developments on physical activity looking at the challenges and opportunities they pose. Key elements of the WHO's Global Strategy on Diet, Physical Activity and Health (GSDPAH) are summarised, focusing specifically on the physical activity components, and by drawing upon recent fora (Atlanta, October 2002; Miami, December 2004; Cascais, February 2005; Beijing, October 2005; Bogotá, November 2005), we outline the barriers and areas of support required for successful development and implementation of national, population-based action on physical activity. These gatherings focused particularly on the needs of developing countries, where to date little has been done to augment physical activity at a population level. Unless swift action is taken, these countries will soon suffer significantly from an increased prevalence of non communicable diseases (NCD). Existing initiatives and opportunities for national and international action on physical activity are identified. Specific actions are proposed for advocacy, communication and dissemination, networks and partnerships, fundraising, policy development and implementation, programme implementation and evaluation, surveillance and capacity building. The development of the Global Alliance for Physical Activity (GAPA) provides a structure for international collaboration.