This article introduces, synthesises, and discusses four articles from four issues of the Journal 'City'. The author argues that while urban and peri-urban agriculture is emerging in almost every city in the world, seeing it as a coherent 'movement' is problematic as it varies so widely in its form, its motivation and its aims between countries and continents. It is also often unable to stop the increasing control of urban land by wealthy urban elites. Nevertheless, urban agriculture has a major role to play in achieving food security for the world's poor, and needs to be recognised as an international trend of rapidly growing importance. The author argues that the Transition Movement has played a key role in supporting some of these initiatives.