This IDS Bulletin explores recent evidence on integrated approaches in rural development. Since the 1970s, holistic and multisectoral programming has been based on the synergistic potential of achieving more through a ‘big push’ of doing lots together. The Sustainable Development Goals (SDGs) also suggest a greater need to understand and address interconnectedness across different sectors. Drawing extensively on a recent impact evaluation of the Millennium Villages Project in northern Ghana, this issue presents a series of articles on the challenges of evaluating integrated development. The articles explore the challenge of assessing synergy; the cost-effectiveness of integration; the value of mixing methods; and dealing with multiple outcomes on different timelines. This introduction concludes by suggesting a narrower testing of combinations of interventions in different contexts, and incrementally building the evidence base; rather than ‘doing everything together’, where a lack of impact combined with weak mid-range theory can limit learning about what works and why.