In the past 20 years, the number of surgical procedures carried out on a day care basis has steadily grown in European countries. Advances in medical technologies, particularly the diffusion of less invasive surgical interventions, and better anaesthetics have made this development possible. These innovations have improved effectiveness and patient safety. They also help to reduce the unit cost of interventions by shortening the length of stay. However, the overall impact on cost depends on the extent to which any greater use of these procedures may be offset by a reduction in unit cost, taking into account the cost of post-acute care and community health services.