Climate change can appear remote compared with problems such as poverty, disease and economic stagnation. Development planners are often unsure how it will affect their work, and whether and how to integrate or “mainstream” climate change considerations within their activities. Climate change is in fact intricately tied to many development objectives. Furthermore, how development occurs has implications for climate change as well as the vulnerability of societies to its impacts. This chapter outlines the links between climate change and development. It defines key concepts including weather, climate variability and climate change, and response measures, particularly adaptation to climate change impacts and mitigation of greenhouse gas emissions. The chapter then outlines the framework of case studies of Bangladesh, Egypt, Fiji, Nepal, Tanzania and Uruguay, which were conducted as part of an OECD project on mainstreaming responses to climate change in development planning and assistance.