In the past few decades, the number of surgical procedures carried out on a same‑day basis has markedly increased in OECD countries. Advances in medical technologies – in particular the diffusion of less invasive surgical interventions – and better anaesthetics have made this development possible. These innovations have improved patient safety and health outcomes. Further, by shortening the treatment episode, ambulatory surgery can save important resources without any adverse effects on quality of care. It also frees up capacity within hospitals to focus on more complex cases or to reduce waiting lists. However, the impact of the rise in same‑day surgery on overall health spending may not be straightforward, since the reduction in unit costs (compared to inpatient surgery) may be offset by overall growth in the volume of procedures performed. Any additional costs related to post-acute care and community health services following the interventions also need to be considered.