The questions of whether aid has impact and is effective have been the subject of considerable attention. This thematic issue brings together nine studies that speak to the diverse ways in which aid affects development outcomes including, but not limited to, growth. It takes stock of what we know about the relationship between aid and growth — including via international trade — and presents new evidence and analysis on core topics comprising aid and maternal mortality, climate change, state fragility, issues of local ownership, donor co-ordination, donor motivations in aid allocation, and the evidence base on ‘thinking and working politically’ in development. While decreasing in relative terms, foreign aid remains an important financial flow for many developing countries. The topic of aid’s impact on growth, therefore, remains central to development research and practice.​​