Challenge to Change supports international development and humanitarian relief agencies to mainstream sustainability into their programme delivery systems. This means minimizing negative social and environmental impacts in the production, supply, use and disposal of goods and services, and going further where possible by harnessing those systems to generate positive impacts – a ‘regenerative’ approach. Most development and relief programmes have significant greenhouse gas emissions, water footprints and other overlooked negative consequences. Challenge to Change utilizes the unique characteristics of development and aid programmes, to promote the circular use of resources and so to minimize waste, and to build sustainability into new programme interventions by innovating at the design stage. We use systems models to identify the best intervention points, and we always promote participatory approaches to accelerate change. We work with government agencies, multilateral and bilateral organisations and NGOs, engaging managers and staff, and encouraging the engagement of beneficiary communities as key stakeholders when appropriate.