Historically simulation was used as an education and training technique in healthcare, but now has an emerging role in improving quality and safety. Simulation-based techniques can be applied to help understand healthcare settings and the practices and behaviours of those who work in them. Simulation-based interventions can help to improve care and outcomes – for example, by improving readiness of teams to respond effectively to situations or to improve skill and speed. Simulation can also help test planned interventions and infrastructural changes, allowing possible vulnerabilities and risks to be identified and addressed. Challenges include cost, resources, training, and evaluation, and the lack of connection between the simulation and improvement fields, both in practice and in scholarship. The business case for simulation as an improvement technique remains to be established. This Element concludes by offering a way forward for simulation in practice and for future scholarly directions to improve the approach. This title is also available as Open Access on Cambridge Core.